Merge branch 'jc/po-pritime-fix'

We started using "%" PRItime, imitating "%" PRIuMAX and friends, as a way to format the internal timestamp value, but this does not play well with gettext(1) i18n framework, and causes "make pot" that is run by the l10n coordinator to create a broken po/git.pot file. This is a possible workaround for that problem. * jc/po-pritime-fix: Makefile: help gettext tools to cope with our custom PRItime format