Don't mark realloc with __attribute__((malloc))

According to
http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html

realloc should NOT be marked with __attribute__((malloc)). Quoting:

   realloc-like functions do not have this property as the memory
   pointed to does not have undefined content.

For reference, __mallocfunc is defined in sys/cdefs.h as:

    #define __mallocfunc  __attribute__((malloc))

Change-Id: I56083542ba92e4608dd7c55fb5596a138eb50cc9

libc/include/malloc.h

@@ -35,7 +35,7 @@ __BEGIN_DECLS
 
 extern __mallocfunc void*  malloc(size_t);
 extern __mallocfunc void*  calloc(size_t, size_t);
-extern __mallocfunc void*  realloc(void *, size_t);
+extern void*  realloc(void *, size_t);
 extern                void   free(void *);
 
 extern void*   memalign(size_t  alignment, size_t  bytesize);