Remove vsnprintf() and strtoumax() validation.

Remove code that validates malloc_vsnprintf() and malloc_strtoumax()
against their namesakes.  The validation code has adequately served its
usefulness at this point, and it isn't worth dealing with the different
formatting for %p with glibc versus other implementations for NULL
pointers ("(nil)" vs. "0x0").

Reported by Mike Hommey.

include/jemalloc/internal/jemalloc_internal.h.in

@@ -374,8 +374,6 @@ extern malloc_mutex_t	arenas_lock; /* Protects arenas initialization. */
 extern arena_t		**arenas;
 extern unsigned		narenas;
 
-extern bool		malloc_initialized;
-
 arena_t	*arenas_extend(unsigned ind);
 void	arenas_cleanup(void *arg);
 arena_t	*choose_arena_hard(void);