put CURL related functions into a separate file

src/helpers.cpp

@@ -408,12 +408,3 @@ std::basic_string<my_char_t> Scroller(const std::basic_string<my_char_t> &str, s
 	return result;
 }
 
-#ifdef HAVE_CURL_CURL_H
-size_t write_data(char *buffer, size_t size, size_t nmemb, void *data)
-{
-	size_t result = size*nmemb;
-	static_cast<std::string *>(data)->append(buffer, result);
-	return result;
-}
-#endif // HAVE_CURL_CURL_H
-