Pull out arena_bin_info_t and arena_bin_t into their own file.

In the process, kill arena_bin_index, which is unused.  To follow are several
diffs continuing this separation.

src/bin.c

@@ -0,0 +1,21 @@
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+#include "jemalloc/internal/bin.h"
+
+const bin_info_t bin_infos[NBINS] = {
+#define BIN_INFO_bin_yes(reg_size, slab_size, nregs)			\
+	{reg_size, slab_size, nregs, BITMAP_INFO_INITIALIZER(nregs)},
+#define BIN_INFO_bin_no(reg_size, slab_size, nregs)
+#define SC(index, lg_grp, lg_delta, ndelta, psz, bin, pgs,		\
+    lg_delta_lookup)							\
+	BIN_INFO_bin_##bin((1U<<lg_grp) + (ndelta<<lg_delta),		\
+	    (pgs << LG_PAGE), (pgs << LG_PAGE) / ((1U<<lg_grp) +	\
+	    (ndelta<<lg_delta)))
+	SIZE_CLASSES
+#undef BIN_INFO_bin_yes
+#undef BIN_INFO_bin_no
+#undef SC
+};
+
+