gettext: always use UTF-8 on native Windows

Git on native Windows exclusively uses UTF-8 for console output (both with
MinTTY and native Console windows). Gettext uses setlocale() to determine
the output encoding for translated text, however, MSVCRT's setlocale()
doesn't support UTF-8. As a result, translated text is encoded in system
encoding (GetAPC()), and non-ASCII chars are mangled in console output.

Use gettext's bind_textdomain_codeset() to force the encoding to UTF-8 on
native Windows.

In this developers' setup, HAVE_LIBCHARSET_H is apparently defined, but
we *really* want to override the locale_charset() here.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

gettext.c

@@ -12,7 +12,9 @@
 #ifndef NO_GETTEXT
 #	include <locale.h>
 #	include <libintl.h>
-#	ifdef HAVE_LIBCHARSET_H
+#	ifdef GIT_WINDOWS_NATIVE
+#		define locale_charset() "UTF-8"
+#	elif defined HAVE_LIBCHARSET_H
 #		include <libcharset.h>
 #	else
 #		include <langinfo.h>