refactor the algorithm for testing the cors

while here:
- send cors headers even if the status is 404
- add: access_control_expose_headers config option - list of additional headers sent in Access-Control-Expose-Headers
- add: access_control_allow_credentials config option - if true return Access-Control-Allow-Credentials header equal "true"

winixd/functions/functionbase.h

@@ -111,6 +111,8 @@ public:
 
 	virtual bool HasAccess();
 
+	virtual void AddAllowMethodsHeader();
+
 	virtual bool IsCorsMethodAvailable(Request::Method method);
 	virtual bool IsCorsOriginAvailable(const std::wstring & origin_url);
 	virtual bool AreCorsCredentialsAvailable();
@@ -121,6 +123,11 @@ public:
 	virtual void AddAccessControlAllowHeadersHeader(const std::wstring & headers);
 	virtual void AddAccessControlMaxAgeHeader();
 	virtual void AddAccessControlAllowCredentialsHeader();
+	virtual void AddAccessControlExposeHeadersHeader();
+	virtual void AddCorsPreflightRequestHeaders(const std::wstring & origin, Request::Method method, const std::wstring * request_headers);
+	virtual void AddCorsNormalRequestHeaders(const std::wstring & origin);
+	virtual void AddResponseHeadersForOrigin(const std::wstring & origin);
+	virtual void CheckOriginHeader();
 
 
 	virtual void MakeGet();