Log Message:
tex-l3kernel{,-doc},tex-l3experimental: update to 2018.49853

## [2019-01-28]

### Added

- Global versions of box affine functions, e.g. `\box_grotate:Nn`
- Global versions of box size adjustment functions
- `\box_(g)set_eq_drop:NN`, `\(h|v)box_unpack_drop:N`
- `\file_get:nnN` and `\file_get:nnNTF`
- Experimental functions `\sys_shell_get:nnN` and `\sys_shell_get:nnNTF`

### Changed

- `\char_generate:nn` now always takes exactly two expansions
- Move `\prg_generate_conditional_variant:Nnn` to stable
- Renamed experimental `\box_trim:Nnnnn` and `\box_viewport:Nnnnn` as
  `\box_set_trim:Nnnnn` and `\box_set_viewport:Nnnnn`, respectively

### Deprecated

- `\box_(g)set_eq_clear:NN`, replaced by `\box_(g)set_eq_drop:NN`
- `\(h|v)box_unpack_clear:N`, replaced by `\(h|v)box_unpack_drop:N
- `\tl_(g)set_from_file(_x):Nnn`, replaced by `\file_get:nnN`

### Fixed

- Scope treatment of `\box_set_dp:N`, _etc._
- In (u)platex: detection of spaces in `\tl_rescan:nn` and related
  functions

### Removed

- Experimental function family `\tl_(g)set_from_shell:(N|c)nn`
  (replaced by `\sys_shell_get:nnN`)