QTfrontend: Fix flickering and bad offset of control config popup If you opened the pop-up to change a key, there was a very short flicker at the left side and the pop-up had a bad offset which sometimes caused entries to be out of screen bounds.

void fpcrtl_halt(int num) {
    __coverity_panic__();
}

int fpcrtl_abs(int num) {
    return num >= 0 ? num : -num;
}