Changes with nginx 1.5.4 27 Aug 2013
*) Change: now the "image_filter" directive with the "size" parameter returns responses with the "application/json" MIME type.
*) Feature: the ngx_http_auth_request_module.
*) Bugfix: a segmentation fault might occur on start or during reconfiguration if the "try_files" directive was used with an empty parameter.
*) Bugfix: memory leak if relative paths were specified using variables in the "root" or "auth_basic_user_file" directives.
*) Bugfix: the "valid_referers" directive incorrectly executed regular expressions if a "Referer" header started with "https://". Thanks to Liangbin Li.
*) Bugfix: responses might hang if subrequests were used and an SSL handshake error happened during subrequest processing. Thanks to Aviram Cohen.
*) Bugfix: in the ngx_http_autoindex_module.
*) Bugfix: in the ngx_http_spdy_module.