Log Message:
Update to 1.4.19. From the changelog:

documentation:

* configure: Add missing AC_ARG_VAR for all programs so that they are
  documented in --help output, and so that autoconf knows they are \ 
"precious"
  and preserves them if configure is rerun even when they're specified via an
  environment variable.

* Add usage examples for $jsonobject.

* Fix path to omega in quickstart document.  Fixes #813, reported by Jim Lynch.

* Update for the IRC channel move from freenode to libera.chat.

indexers:

* Fix handling of UTF-16 BOMs in XML and HTML - we had the sense of the
  endianness indicated by the BOM the wrong way round.

* Avoid making an extra temporary copy of HTML/XML data which has a UTF16 BOM.

* We now ignore an end of line immediately after a PHP close tag to match what
  PHP does.

* omindex:

  + Fix handling of formatted xlsx dates in certain cases.

* scriptindex:

  + Add new scriptindex whitespace removal actions `ltrim`, `rtrim`, `squash`,
    and `trim`.

  + Improve `truncate` action - if a word ends exactly on the requested length
    we now leave it in place rather than removing it.

  + Report the location of previous `unique` action in the error given when
    `unique` is used more than once.

omega:

* Clamp START and END with packed timestamps.  The 4-byte unsigned packed
  time_t format can't represent dates before 1970 or after Sun 07 Feb 2106
  06:28:15 UTC so clamp dates before or after these - previously they would
  wrap around.

* The JSON produced by $jsonobject no longer contains newlines, which makes it
  usable as a single line serialisation format without post-processing.

* Add $base64 OmegaScript command.

* omega: Add flag_no_positions to wrap new
  Xapian::QueryParser::FLAG_NO_POSITIONS.

templates:

* Fix topterms template to not trigger early matching.  We were checking $msize
  before including the `query` template, but doing so would trigger the query
  to be run, which means that settings early in the `query` template which
  should affect the result (such as $setmap{prefix,...}) were being ignored
  when the `topterms` template was used.  Partly addresses #815, reported by
  Gennadiy.

* Add field support to opensearch and xml templates.  These templates now also
  search title, topic and filename by default and support `title:`, `author:`
  and `topic:` in the query string (both like the template `query` already
  does). Fixes remaining issue in #815, reported by Gennadiy.

testsuite:

* Expand omegatest.  All scriptindex actions now have test coverage.

build system:

* Replace uses of obsolete autoconf macros, fixing warnings if configure is
  regenerated with a recent release of autoconf.

portability:

* Don't automatically use _FORTIFY_SOURCE on mingw-w64.  Recent mingw-w64
  versions require -lssp to be linked when _FORTIFY_SOURCE is enabled, so just
  skip the automatic enabling.  Users who want to enable it can specify it
  explicitly.

  Fixes #808, reported by xpbxf4.

* Automatically enable GCC warnings -Wduplicated-cond and -Wduplicated-branches
  if using a GCC version new enough to support them.  The usefulness of
  -Wduplicated-cond was highlighted by dcb in #816.

* Fix GCC -Wshadow warning.

* Use clock_gettime() and nanosleep() under modern mingw as these allow higher
  precision than what we previously used.