Log Message:
nim: Update to 1.2.6

Changelog extracted from the unspecific changelog.md on the 1.2.6 tag.
Unable to get a Changelog diff for 1.2.4 and 1.2.6.

# v1.4.0 - yyyy-mm-dd

## Standard library additions and changes

  For `net` and `nativesockets`, an `inheritable` flag has been added to all
  `proc`s that create sockets, allowing the user to control whether the
  resulting socket is inheritable. This flag is provided to ease the writing of
  multi-process servers, where sockets inheritance is desired.

  For a transistion period, define `nimInheritHandles` to enable file handle
  inheritance by default. This flag does **not** affect the `selectors` module
  due to the differing semantics between operating systems.

  `system.setInheritable` and `nativesockets.setInheritable` is also introduced
  for setting file handle or socket inheritance. Not all platform have these
  `proc`s defined.

- The file descriptors created for internal bookkeeping by `ioselector_kqueue`
  and `ioselector_epoll` will no longer be leaked to child processes.

- `strutils.formatFloat` with `precision = 0` has been restored to the version
  1 behaviour that produces a trailing dot, e.g. `formatFloat(3.14159, precision \ 
= 0)`
  is now `3.`, not `3`.
- `critbits` adds `commonPrefixLen`.

- `relativePath(rel, abs)` and `relativePath(abs, rel)` used to silently give \ 
wrong results
  (see #13222); instead they now use `getCurrentDir` to resolve those cases,
  and this can now throw in edge cases where `getCurrentDir` throws.
  `relativePath` also now works for js with `-d:nodejs`.

- JavaScript and NimScript standard library changes: `streams.StringStream` is
  now supported in JavaScript, with the limitation that any buffer `pointer`s
  used must be castable to `ptr string`, any incompatible pointer type will not
  work. The `lexbase` and `streams` modules used to fail to compile on
  NimScript due to a bug, but this has been fixed.

  The following modules now compile on both JS and NimScript: `parsecsv`,
  `parsecfg`, `parsesql`, `xmlparser`, `htmlparser` and `ropes`. Additionally
  supported for JS is `cstrutils.startsWith` and `cstrutils.endsWith`, for
  NimScript: `json`, `parsejson`, `strtabs` and `unidecode`.

- Added `streams.readStr` and `streams.peekStr` overloads to
  accept an existing string to modify, which avoids memory
  allocations, similar to `streams.readLine` (#13857).

- Added high-level `asyncnet.sendTo` and `asyncnet.recvFrom`. UDP functionality.

- `paramCount` & `paramStr` are now defined in os.nim instead of \ 
nimscript.nim for nimscript/nimble.
- `dollars.$` now works for unsigned ints with `nim js`

- Improvements to the `bitops` module, including bitslices, non-mutating versions
  of the original masking functions, `mask`/`masked`, and varargs support for
  `bitand`, `bitor`, and `bitxor`.

- `sugar.=>` and `sugar.->` changes: Previously `(x, y: int)` was transformed
  into `(x: auto, y: int)`, it now becomes `(x: int, y: int)` in consistency
  with regular proc definitions (although you cannot use semicolons).

  Pragmas and using a name are now allowed on the lefthand side of `=>`. Here
  is an aggregate example of these changes:
  ```nim
  import sugar

  foo(x, y: int) {.noSideEffect.} => x + y

  # is transformed into

  proc foo(x: int, y: int): auto {.noSideEffect.} = x + y
  ```
- The fields of `times.DateTime` are now private, and are accessed with getters \ 
and deprecated setters.

- The `times` module now handles the default value for `DateTime` more \ 
consistently. Most procs raise an assertion error when given
  an uninitialized `DateTime`, the exceptions are `==` and `$` (which returns \ 
`"Uninitialized DateTime"`). The proc `times.isInitialized`
  has been added which can be used to check if a `DateTime` has been initialized.

- Fix a bug where calling `close` on io streams in osproc.startProcess was a \ 
noop and led to
  hangs if a process had both reads from stdin and writes (eg to stdout).

- The callback that is passed to `system.onThreadDestruction` must now be \ 
`.raises: []`.
- The callback that is assigned to `system.onUnhandledException` must now be \ 
`.gcsafe`.

- `osproc.execCmdEx` now takes an optional `input` for stdin, `workingDir` and `env`
  parameters.

- Added a `ssl_config` module containing lists of secure ciphers as recommended by
  [Mozilla OpSec](https://wiki.mozilla.org/Security/Server_Side_TLS)

- `net.newContext` now defaults to the list of ciphers targeting
  ["Intermediate \ 
compatibility"](https://wiki.mozilla.org/Security/Server_Side_TLS#Intermediate_compatibility_.28recommended.29)
  per Mozilla's recommendation instead of `ALL`. This change should protect
  users from the use of weak and insecure ciphers while still provides
  adequate compatibility with the majority of the Internet.

- A new module `std/jsonutils` with hookable `jsonTo,toJson,fromJson` operations \ 
for json
  serialization/deserialization of custom types was added.

- A new proc `heapqueue.find[T](heap: HeapQueue[T], x: T): int` to get index of \ 
element ``x``
  was added.
- Added `rstgen.rstToLatex` convenience proc for `renderRstToOut` and \ 
`initRstGenerator`
  with `outLatex` output.
- Added `os.normalizeExe`, e.g.: `koch` => `./koch`.
- `macros.newLit` now preserves named vs unnamed tuples; use \ 
`-d:nimHasWorkaround14720`
  to keep old behavior.
- Added `random.gauss`, that uses the ratio of uniforms method of sampling from \ 
a Gaussian distribution.
- Added `typetraits.elementType` to get element type of an iterable.
- `typetraits.$` changes: `$(int,)` is now `"(int,)"` instead of \ 
`"(int)"`;
  `$tuple[]` is now `"tuple[]"` instead of `"tuple"`;
  `$((int, float), int)` is now `"((int, float), int)"` instead of \ 
`"(tuple of (int, float), int)"`
- Added `macros.extractDocCommentsAndRunnables` helper

- `strformat.fmt` and `strformat.&` support `= specifier`. \ 
`fmt"{expr=}"` now
  expands to `fmt"expr={expr}"`.
- deprecations: `os.existsDir` => `dirExists`, `os.existsFile` => `fileExists`

- Added `jsre` module, [Regular Expressions for the JavaScript \ 
target.](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions)
- Made `maxLines` argument `Positive` in `logging.newRollingFileLogger`,
  because negative values will result in a new file being created for each logged
  line which doesn't make sense.
- Changed `log` in `logging` to use proper log level on JavaScript target,
  e.g. `debug` uses `console.debug`, `info` uses `console.info`, `warn` uses \ 
`console.warn`, etc.
- Tables, HashSets, SharedTables and deques don't require anymore that the passed
  initial size must be a power of two - this is done internally.
  Proc `rightSize` for Tables and HashSets is deprecated, as it is not needed \ 
anymore.
  `CountTable.inc` takes `val: int` again not `val: Positive`; I.e. it can \ 
"count down" again.
- Removed deprecated symbols from `macros` module, deprecated as far back as `0.15`.

## Language changes
- In newruntime it is now allowed to assign discriminator field without \ 
restrictions as long as case object doesn't have custom destructor. \ 
Discriminator value doesn't have to be a constant either. If you have custom \ 
destructor for case object and you do want to freely assign discriminator \ 
fields, it is recommended to refactor object into 2 objects like this:
  ```nim
  type
    MyObj = object
      case kind: bool
        of true: y: ptr UncheckedArray[float]
        of false: z: seq[int]

  proc `=destroy`(x: MyObj) =
    if x.kind and x.y != nil:
      deallocShared(x.y)
      x.y = nil
  ```
  Refactor into:
  ```nim
  type
    MySubObj = object
      val: ptr UncheckedArray[float]
    MyObj = object
      case kind: bool
      of true: y: MySubObj
      of false: z: seq[int]

  proc `=destroy`(x: MySubObj) =
    if x.val != nil:
      deallocShared(x.val)
      x.val = nil
  ```