Determine rtree levels at compile time.

Rather than dynamically building a table to aid per level computations,
define a constant table at compile time.  Omit both high and low
insignificant bits.  Use one to three tree levels, depending on the
number of significant bits.

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -22,6 +22,13 @@
  */
 #undef CPU_SPINWAIT
 
+/*
+ * Number of significant bits in virtual addresses.  This may be less than the
+ * total number of bits in a pointer, e.g. on x64, for which the uppermost 16
+ * bits are the same as bit 47.
+ */
+#undef LG_VADDR
+
 /* Defined if C11 atomics are available. */
 #undef JEMALLOC_C11ATOMICS