git-gui: Mark revision chooser tooltip for translation

git-gui: Mark revision chooser tooltip for translation

Someone on #git today pointed out that the revision chooser's tooltips
are were being drawn with untranslated strings for the fixed labels we
include, such as "updated", "commit" and "remote".  These strings are
now passed through mc to allow them to be localized.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>