wt-status: turn advice_status_hints into a field of wt_status

No behavior change in this patch, but this makes the display of status
hints more flexible as they can be enabled or disabled for individual
calls to commit.c:run_status().

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit.c b/builtin/commit.c
index 94512c0..28c6309 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -169,6 +169,7 @@
 	gitmodules_config();
 	git_config(fn, s);
 	determine_whence(s);
+	s->hints = advice_status_hints; /* must come after git_config() */
 }
 
 static void rollback_index_files(void)