htmldoc-x11: update to 1.9.11.

ChangeLog:

# Changes in HTMLDOC v1.9.11

- Added high-resolution desktop icons for Linux.
- Updated the internal HTTP library to fix truncation of redirection URLs
  (Issue #396)
- Fixed a regression in the handling of character entities for UTF-8 input
  (Issue #401)
- The `--numbered` option did not work when the table-of-contents was disabled
  (Issue #405)

# Changes in HTMLDOC v1.9.10

- Updated local zlib to v1.2.11.
- Updated local libpng to v1.6.37.
- Fixed packaging issues on macOS and Windows (Issue #377, Issue #386)
- Now ignore sRGB profile errors in PNG files (Issue #390)
- The GUI would crash when saving (Issue #391)
- Page comments are now allowed in `pre` text (Issue #394)

# Changes in HTMLDOC v1.9.9

- Fixed a redirection issue - some sites (incorrectly) provide an incomplete
  Location: URL in the HTTP response.
- Fixed https: support on newer versions of Windows (Issue #378)
- Fixed a problem with remote URLs containing spaces (Issue #379)
- Fixed a UTF-8 processing bug for Markdown files (Issue #383)
- Added support for `<FONT FACE="monospace">` (Issue #385)


(fcambus)