Update third-party headers_more module from 0.15 to 0.16.
* bugfix: the on-demand handler/filter registration mechanism did
not work fully for config reload via the HUP signal.
* bugfix: when setting a multi-value response header to a single
value, the single value might be repeated on each old value.
* feature: added some debugging outputs that can be enabled by
the --with-debug option when building nginx or ngx_openresty.
* bugfix: we should set header hash using ngx_hash_key_lc, not
simply to 1.
* bugfix: Setting Cache-Control response headers might not work
with other nginx output filter modules because we did not
properly prepare the r->cache_control array at the same time.
* bugfix: more_set_input_headers and more_clear_input_headers did
not handle the Accept-Encoding request headers properly.
* bugfix: the more_set_input_headers directive might cause invalid
memory reads because Nginx request header values must be null
terminated. thanks Maxim Dounin.
* bugfix: removing builtin headers in huge request headers with 20+
entries could result in data loss. thanks Chris Dumoulin for the
patch in github issue #6.