add a Request::raw_post buffer

This buffer is used when a Function::NeedToCopyRawPost() method returned true.

while here:
- remove WINIX_POST_PARAMS and WINIX_RAW_POST_STRING plugin messages

winixd/core/app.h

@@ -128,7 +128,6 @@ private:
 	PostParser post_parser;
 	PostMultiParser post_multi_parser;
 	pt::SpaceParser space_parser;
-	pt::TextStream post_buffer;
 
 	CookieParser cookie_parser;
 	AcceptBaseParser accept_base_parser;
@@ -200,7 +199,7 @@ private:
 	bool SaveEnvHTTPVariable(const char * env);
 	void ReadInputPostToBuffer();
 	void ParsePostJson();
-	void ReadPostJson();
+	void ReadPostJson(bool copy_raw_post);
 	void ReadPostVars();
 	void CheckIE();
 	void CheckKonqueror();