Log Message:
Update tex-l3{experimental,kernel,packages}{,-doc} to 2017.44864

 - New \hbox_set_to_wd:Nnw and \vbox_set_to_ht:Nnw functions
 - Revised l3file module to give better defined
   path/file/extension split
 - New experimental functions in l3file: \file_input_stop:,
   \file_get_mdfive_hash:nN, \file_get_size:nN and
   \file_get_timestamp:nN; currently XeTeX does not support
   getting file size/timestamp
 - New experimental \mode_leave_vertical: as a code-level
   equivalent of \leavevmode
 - New experimental support for shell escape in l3sys module
 - New mechanism for checking variable declarations locally:
   see option "enable-debug" and
   \debug_check_declarations_(on|off):
 - More invalid regex patterns trapped with warning
 - More regex documentation examples
 - Bug fix for \tl_mixed_case:n(n) with pdfTeX when the first
   character is outside the ASCII range
 - Fix nesting of selective setting in l3keys