gettextize: git-init "Initialized [...] repository" message

gettextize: git-init "Initialized [...] repository" message

Change the git-init "Initialized empty Git repository" message and its
variants to use gettext.

This is one of the messages that could do with splitting up, I had a
WIP patch to do that that began like this:

    const char *reinit_shared   = _("Reinitialized existing shared Git repository in %s\n");
    const char *init_shared	    = _("Initialized empty shared Git repository in %s\n");
    const char *reinit_noshared = _("Reinitialized existing Git repository in %s\n");
    const char *init_noshared   = _("Initialized empty Git repository in %s\n");

But in the first round of gettextization I'm aiming to keep code
changes to a minimum for ease of review.

We can solicit input from translators about which messages that use
too much sprintf-ing are troublesome, and change those later.

Note that the TRANSLATORS comment doesn't use the usual Git
style. This is because everything from "/* TRANSLATORS: " to "*/" will
extracted as-is xgettext(1) and presented to translators, including
newlines and leading "*"'s. There seems to be no way to change that,
short of patching xgettext itself.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>