Convert rtree from (void *) to (uint8_t) storage.

Reduce rtree memory usage by storing booleans (1 byte each) rather than
pointers.  The rtree code is only used to record whether jemalloc manages
a chunk of memory, so there's no need to store pointers in the rtree.

Increase rtree node size to 64 KiB in order to reduce tree depth from 13
to 3 on 64-bit systems.  The conversion to more compact leaf nodes was
enough by itself to make the rtree depth 1 on 32-bit systems; due to the
fact that root nodes are smaller than the specified node size if
possible, the node size change has no impact on 32-bit systems (assuming
default chunk size).

include/jemalloc/internal/jemalloc_internal.h.in

@@ -853,7 +853,7 @@ ivsalloc(const void *ptr, bool demote)
 {
 
 	/* Return 0 if ptr is not within a chunk managed by jemalloc. */
-	if (rtree_get(chunks_rtree, (uintptr_t)CHUNK_ADDR2BASE(ptr)) == NULL)
+	if (rtree_get(chunks_rtree, (uintptr_t)CHUNK_ADDR2BASE(ptr)) == 0)
 		return (0);
 
 	return (isalloc(ptr, demote));