git-gui: Make the statistics of po2msg match those of msgfmt

git-gui: Make the statistics of po2msg match those of msgfmt

The strings we were showing from po2msg didn't exactly match those
of msgfmt's --statistics output so we didn't show quite the same
results when building git-gui's message files.  Now we're closer
to what msgfmt shows (at least for an en_US locale) so the make
output matches.

I noticed that the fuzzy translation count is off by one for the
current po/zh_cn.po file.  Not sure why and I'm not going to try
and debug it at this time as the po2msg is strictly a fallback,
users building from source really should prefer msgfmt.

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