Ghostscript no longer supports UTF-16-BE-hex strings as a way of
supplying Unicode data in pdfmark so we have lost this functionality too:
http://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=e997c6836d243ab37fe3a5f0d57974af95eb5eac
For users this means setting --title, --author, etc. will not work if gs
9.24 is installed, but if the file has existing metadata it might work.
For now we enforce police-state-strict ASCII, until there's time to
implement proper metadata editing. Relevant tests set to xfail.
Related to previous validation issue. If the /CreationDate had no
timezone, Ghostscript also creates invalid metadata. Work around this.
Also fix up PDF date decoding, and transcode dates to standardize them.