i18n: git-add "remove '%s'" message

Make the "remove '%s'" message translatable. It's displayed under `git
add -u --verbose`. Also skip the corresponding test when output is not
in the C locale.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/add.c

@@ -74,7 +74,7 @@ static void update_callback(struct diff_queue_struct *q,
 			if (!(data->flags & ADD_CACHE_PRETEND))
 				remove_file_from_index(&the_index, path);
 			if (data->flags & (ADD_CACHE_PRETEND|ADD_CACHE_VERBOSE))
-				printf("remove '%s'\n", path);
+				printf(_("remove '%s'\n"), path);
 			break;
 		}
 	}

t/t2200-add-update.sh

@@ -111,7 +111,7 @@ test_expect_success 'touch and then add explicitly' '
 
 '
 
-test_expect_success 'add -n -u should not add but just report' '
+test_expect_success C_LOCALE_OUTPUT 'add -n -u should not add but just report' '
 
 	(
 		echo "add '\''check'\''" &&