@brief Get the keycodes attached to a keysyms. There can be several value, so what is returned is an array of keycode terminated by XCB_NO_SYMBOL. You are responsible to free it. Be aware that this function can be slow. It will convert all combinations of all available keycodes to keysyms to find the ones that match. @param syms Key symbols. @param keysym The keysym to look for. @return A XCB_NO_SYMBOL terminated array of keycode, or NULL if nothing is found.