treewide: be explicit about dependence on convert.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/cat-file.c

@@ -7,6 +7,7 @@
 #include "cache.h"
 #include "alloc.h"
 #include "config.h"
+#include "convert.h"
 #include "builtin.h"
 #include "diff.h"
 #include "environment.h"