Merge branch 'ik/gitweb-force-highlight'

"gitweb" can spawn "highlight" to show blob contents with
(programming) language-specific syntax highlighting, but only
when the language is known.  "highlight" can however be told
to make the guess itself by giving it "--force" option, which
has been enabled.

* ik/gitweb-force-highlight:
  gitweb: use highlight's shebang detection
  gitweb: remove unused guess_file_syntax() parameter