jemalloc: Avoid adding bounds unnecessarily

The memory returned by je_allocm() and je_rallocm() is allocated using
je_mallocx() and je_(x|r)allocx(), respectively, and those functions apply
bounds to their return values by virtue of being implemented using
imalloc().

This makes it easier to make jemalloc bound pointers to the usable size
instead of the allocation size.

contrib/jemalloc/src/jemalloc.c

@@ -3848,7 +3848,7 @@ je_allocm(void **ptr, size_t *rsize, size_t size, int flags) {
 	if (rsize != NULL) {
 		*rsize = isalloc(tsdn_fetch(), p);
 	}
-	*ptr = BOUND_PTR(p, size);
+	*ptr = p;
 	return ALLOCM_SUCCESS;
 }
 
@@ -3873,7 +3873,7 @@ je_rallocm(void **ptr, size_t *rsize, size_t size, size_t extra, int flags) {
 	} else {
 		void *p = je_rallocx(*ptr, size+extra, flags);
 		if (p != NULL) {
-			*ptr = BOUND_PTR(p, size+extra);
+			*ptr = p;
 			ret = ALLOCM_SUCCESS;
 		} else {
 			ret = ALLOCM_ERR_OOM;