[SVN] r10102 (Mercurial)

[Frédéric Ballériaux]

Add support for external diff tools.
Tested with Changes (chdiff) and FileMerge (opendiff)

Changed:
U   trunk/Bundles/Mercurial.tmbundle/Commands/Diff Revisions....plist
U   trunk/Bundles/Mercurial.tmbundle/Commands/Diff with Newest (Tip).plist
U   trunk/Bundles/Mercurial.tmbundle/Commands/Diff with Revision….plist
U   trunk/Bundles/Mercurial.tmbundle/Commands/Diff with Working Copy.plist
U   trunk/Bundles/Mercurial.tmbundle/Support/format_status.rb
A   trunk/Bundles/Mercurial.tmbundle/Support/hg_extdiff.rb
U   trunk/Bundles/Mercurial.tmbundle/Support/hg_show_help.rb