Avoid IF-NONE-MATCH in apache_request_headers replacement function
Extract ETag value by RTFM and use correct header name

* See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.19
* Also set 304 not modified, as it's by logic of etags
Merge pull request #77 from garex/issue/fix-etags-processing

Fix etags processing