Optimizing TSD and thread cache layout.

1) Re-organize TSD so that frequently accessed fields are closer to the
beginning and more compact.  Assuming 64-bit, the first 2.5 cachelines now
contains everything needed on tcache fast path, expect the tcache struct itself.

2) Re-organize tcache and tbins.  Take lg_fill_div out of tbin, and reduce tbin
to 24 bytes (down from 32). Split tbins into tbins_small and tbins_large, and
place tbins_small close to the beginning.

include/jemalloc/internal/rtree_structs.h

@@ -53,9 +53,6 @@ struct rtree_ctx_cache_elm_s {
 };
 
 struct rtree_ctx_s {
-#ifndef _MSC_VER
-	JEMALLOC_ALIGNED(CACHELINE)
-#endif
 	rtree_ctx_cache_elm_t	cache[RTREE_CTX_NCACHE];
 };