Add memory utilization analytics to mallctl

The analytics tool is put under experimental.utilization namespace in
mallctl.  Input is one pointer or an array of pointers and the output
is a list of memory utilization statistics.

include/jemalloc/internal/extent_structs.h

@@ -228,4 +228,25 @@ struct extents_s {
 	bool			delay_coalesce;
 };
 
+/*
+ * The following two structs are for experimental purposes. See
+ * experimental_utilization_query_ctl and
+ * experimental_utilization_batch_query_ctl in src/ctl.c.
+ */
+
+struct extent_util_stats_s {
+	size_t nfree;
+	size_t nregs;
+	size_t size;
+};
+
+struct extent_util_stats_verbose_s {
+	void *slabcur_addr;
+	size_t nfree;
+	size_t nregs;
+	size_t size;
+	size_t bin_nfree;
+	size_t bin_nregs;
+};
+
 #endif /* JEMALLOC_INTERNAL_EXTENT_STRUCTS_H */