Introduce hpdata_t.

Using an edata_t both for hugepages and the allocations within those hugepages
was convenient at first, but has outlived its usefulness.  Representing
hugepages explicitly, with their own data structure, will make future
development easier.

src/hpdata.c

@@ -0,0 +1,18 @@
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+#include "jemalloc/internal/hpdata.h"
+
+static int
+hpdata_age_comp(const hpdata_t *a, const hpdata_t *b) {
+	uint64_t a_age = hpdata_age_get(a);
+	uint64_t b_age = hpdata_age_get(b);
+	/*
+	 * hpdata ages are operation counts in the psset; no two should be the
+	 * same.
+	 */
+	assert(a_age != b_age);
+	return (a_age > b_age) - (a_age < b_age);
+}
+
+ph_gen(, hpdata_age_heap_, hpdata_age_heap_t, hpdata_t, ph_link, hpdata_age_comp)