add some hooks to be able to cache hits to googles online mp3 apis with…

add some hooks to be able to cache hits to googles online mp3 apis with mod_httapi e.g. http://(ext=mp3,user_agent='Mozilla/5.0 (X11; Linux x86_64; rv:9.0.1) Gecko/20100101 Firefox/9.0.1')translate.google.com/translate_tts?q=this+is+a+test

src/mod/applications/mod_httapi/mod_httapi_doc.txt

@@ -300,7 +300,7 @@ cookie-file                     : <string>              ""              Path to
 enable-post-var                 : <param_name>          ""              Specify specifc param names ok to send.
 bind-local                      : <string>              ""              Interface to bind to.
 default-profile                 : <string>              default         Profile to use when not specified.
-
+user-agent			: <string>		mod_httapi/1.0	User Agent header value.
 
 
 <permissions>: * = default