Fix the newly-introduced warning and turn on -Werror.

I cleaned up most of our warnings last week but forgot to turn on -Werror,
so of course we're getting new warnings already. I've left -Werror commented
out in those places where we still have warnings to deal with before we can
turn on -Werror.

Change-Id: Ia58ff8b8c1ada4bf81eec6f19ec1d34e133cf4b1
diff --git a/libc/stdio/local.h b/libc/stdio/local.h
index 907fd21..7afa761 100644
--- a/libc/stdio/local.h
+++ b/libc/stdio/local.h
@@ -63,10 +63,7 @@
 int	__vfwprintf(FILE * __restrict, const wchar_t * __restrict, __va_list);
 int	__vfwscanf(FILE * __restrict, const wchar_t * __restrict, __va_list);
 
-/*
- * Function to clean up streams, called from abort() and exit().
- */
-extern void (*__cleanup)(void);
+extern void __atexit_register_cleanup(void (*)(void));
 extern int __sdidinit;
 
 /*