core: fix bypassing of mod_headers rules via chunked requests (CVE-2013-5704)
    
    - mod_cache: fix NULL pointer dereference on empty Content-Type (CVE-2014-3581)
    - mod_proxy_fcgi: fix a potential crash with long headers (CVE-2014-3583)
    - mod_lua: fix handling of the Require line when a LuaAuthzProvider is used
      in multiple Require directives with different arguments (CVE-2014-8109)