nginx 1.7.2 mainline

*) Feature: the "hash" directive inside the "upstream" block.
*) Feature: defragmentation of free shared memory blocks.
    Thanks to Wandenberg Peixoto and Yichun Zhang.
*) Bugfix: a segmentation fault might occur in a worker process if the
default value of the "access_log" directive was used; the bug had
appeared in 1.7.0.
   Thanks to Piotr Sikora.
*) Bugfix: trailing slash was mistakenly removed from the last
parameter of the "try_files" directive.
*) Bugfix: nginx could not be built on OS X in some cases.
*) Bugfix: in the ngx_http_spdy_module.

Changelog: http://nginx.org/en/CHANGES