Fix FTBFS with -no-xkb

The analogue of XkbKeycodeToKeysym() used to be XKeycodeToKeysym(), but
it was deprecated in favour of XGetKeyboardMapping() method.

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>
(cherry picked from commit beb37238fa)

src/kernel/qapplication_x11.cpp

@@ -1621,6 +1621,21 @@ static Visual *find_truecolor_visual( Display *dpy, int scr, int *depth, int *nc
     return v;
 }
 
+static KeySym qt_x11_keycode_to_keysym(Display *dpy, KeyCode kc) {
+#ifndef TQT_NO_XKB
+	return XkbKeycodeToKeysym(dpy, kc, 0, 0);
+#else
+	KeySym rv = NoSymbol;
+	int keysyms_per_keycode;
+	KeySym *keysym_p = XGetKeyboardMapping(dpy, kc, 1, &keysyms_per_keycode);
+	if (keysyms_per_keycode>0) { //< Should always be true unless X server is bugged
+		rv = keysym_p[0];
+	}
+	XFree(keysym_p);
+
+	return rv;
+#endif // TQT_NO_XKB
+}
 
 /*****************************************************************************
   tqt_init() - initializes TQt for X11
@@ -2151,8 +2166,7 @@ void tqt_init_internal( int *argcptr, char **argv,
 	    for (maskIndex = 0; maskIndex < 8; maskIndex++) {
 		for (i = 0; i < map->max_keypermod; i++) {
 		    if (map->modifiermap[mapIndex]) {
-			KeySym sym =
-			    XkbKeycodeToKeysym(appDpy, map->modifiermap[mapIndex], 0, 0);
+			KeySym sym = qt_x11_keycode_to_keysym(appDpy, map->modifiermap[ mapIndex ]);
 			if ( qt_alt_mask == 0 &&
 			     ( sym == XK_Alt_L || sym == XK_Alt_R ) ) {
 			    qt_alt_mask = 1 << maskIndex;
@@ -2181,8 +2195,7 @@ void tqt_init_internal( int *argcptr, char **argv,
 
 		for ( i = 0; i < map->max_keypermod; i++ ) {
 		    if ( map->modifiermap[ mapIndex ] ) {
-			KeySym sym =
-			    XkbKeycodeToKeysym( appDpy, map->modifiermap[ mapIndex ], 0, 0 );
+			KeySym sym = qt_x11_keycode_to_keysym(appDpy, map->modifiermap[ mapIndex ]);
 			if ( sym == XK_Mode_switch ) {
 			    qt_mode_switch_remove_mask |= 1 << maskIndex;
 			}