htmldoc: update to 1.9.12.

# Changes in HTMLDOC v1.9.12

- Fixed a crash bug with "data:" URIs and EPUB output (Issue #410)
- Fixed crash bugs for books (Issue #412, Issue #414)
- Fixed a number-up crash bug (Issue #413)
- Fixed JPEG error handling (Issue #415)
- Fixed crash bugs with bogus table attributes (Issue #416, Issue #417)
- Fixed a crash bug with malformed URIs (Issue #418)
- Fixed a crash bug with malformed GIF files (Issue #423)
- Fixed a crash bug with empty titles (Issue #425)
- Fixed crash bugs with bogus text (Issue #426, Issue #429, Issue #430,
  Issue #431)
- Fixed some issues reported by Coverity.
- Removed the bundled libjpeg, libpng, and zlib.

(fcambus)