Define NO_GETTEXT for Git for Windows

Define NO_GETTEXT for Git for Windows

The dreaded "your vnsprintf is broken (returned -1)" error is back. At
least with the libintl version we have. So for the moment, just work
around the issue by _not_ using gettext.

Ah, I wish that my attempt at implementing a custom strbuf_vaddf() would
not have been brushed aside so rashly. Oh well. Time saved on maintaining
that thing, I guess (although more time went into working around coping
with existing implementations).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>