Use optional zeroing in arena_chunk_alloc() to avoid needless zeroing of
chunks. This is particularly important in the context of swapfile and
DSS allocation, since a long-lived application may commonly recycle
chunks.
Fix a stats bug in large object curruns accounting.
Replace tcache_bin_fill() with arena_tcache_fill(), and fix a bug in an OOM
error path.
Fix API name mangling to coexist with __attribute__((malloc)).
