implement clipboard on iOS

src/util.h

@@ -82,9 +82,6 @@ std::string wstr2str(const std::wstring& wstr);
 bool str_iequals(const std::string& a, const std::string& b);
 std::string str_replace(const std::string& string, const std::string& search, const std::string& replace);
 
-std::string clipboard_get_text();
-bool clipboard_set_text(const std::string& s);
-
 size_t curl_data_handler(void *contents, size_t size, size_t nmemb, void *userp);
 size_t curl_data_write(void *ptr, size_t size, size_t nmemb, FILE *stream);
 void check_OpenGLError(const char* stmt, const char* fname, int line);