gitk: Default to using po2msg.sh if msgfmt doesn't grok --tcl, -l and -d
gitk: Default to using po2msg.sh if msgfmt doesn't grok --tcl, -l and -d

This is a similar change to that submitted by Junio C Hamano for
git-gui.  It tests whether the msgfmt command can be run successfully
with --tcl, -l and -d, and if not, falls back to using po/po2msg.sh.

Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git