gitk: Regenerate .po files

gitk: Regenerate .po files

This is the result of running make update-po and removing or fixing
the strings that were fuzzily matched.  The ones that were fixed were
the ones where the only change was "git rev-list" to "git log", and
the "about gitk" message where the copyright year got updated.

To get xgettext to see the menu labels as needing translation, it
was necessary for arrange for them to be preceded by "mc".  This
therefore changes makemenu to ignore the first element in each
menu item so that it can be "mc" in the makemenu call.

Signed-off-by: Paul Mackerras <paulus@samba.org>