add description parameter to OPT__QUIET

Allows better help text to be defined than "be quiet".  Also make use
of the macro in a place that already had a different description.  No
object code changes intended.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

test-parse-options.c

@@ -68,7 +68,7 @@ int main(int argc, const char **argv)
 		OPT__ABBREV(&abbrev),
 		OPT__VERBOSE(&verbose, "be verbose"),
 		OPT__DRY_RUN(&dry_run, "dry run"),
-		OPT__QUIET(&quiet),
+		OPT__QUIET(&quiet, "be quiet"),
 		OPT_END(),
 	};
 	int i;