i18n: git-merge "Wonderful" message

Gettextize the "Wonderful" message. A test in t7600-merge.sh
explicitly checked for this message. Change it to skip under
GETTEXT_POISON=YesPlease.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/merge.c b/builtin/merge.c
index 4f6b34f..f998206 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -803,7 +803,7 @@
 	struct commit_list *parent = xmalloc(sizeof(*parent));
 
 	write_tree_trivial(result_tree);
-	printf("Wonderful.\n");
+	printf(_("Wonderful.\n"));
 	parent->item = lookup_commit(head);
 	parent->next = xmalloc(sizeof(*parent->next));
 	parent->next->item = remoteheads->item;
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index b147a1b..87d5d78 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -495,7 +495,7 @@
 
 test_debug 'git log --graph --decorate --oneline --all'
 
-test_expect_success 'in-index merge' '
+test_expect_success C_LOCALE_OUTPUT 'in-index merge' '
 	git reset --hard c0 &&
 	git merge --no-ff -s resolve c1 >out &&
 	grep "Wonderful." out &&