winex11: Fix Ctrl+Shift+Tab translation.

dlls/user32/tests/input.c

@@ -1285,6 +1285,8 @@ static void test_ToUnicode(void)
 
     state[VK_SHIFT] |= HIGHEST_BIT;
     state[VK_LSHIFT] |= HIGHEST_BIT;
+    ret = ToUnicode(VK_TAB, SC_TAB, state, wStr, 2, 0);
+    ok(ret == 0, "ToUnicode for CTRL + SHIFT + Tab didn't return 0 (was %i)\n", ret);
     ret = ToUnicode(VK_RETURN, SC_RETURN, state, wStr, 2, 0);
     todo_wine ok(ret == 0, "ToUnicode for CTRL + SHIFT + Return didn't return 0 (was %i)\n", ret);
 }

dlls/winex11.drv/keyboard.c

@@ -2618,7 +2618,7 @@ INT CDECL X11DRV_ToUnicodeEx(UINT virtKey, UINT scanCode, const BYTE *lpKeyState
 #endif
         /* Special case: X turns shift-tab into ISO_Left_Tab. */
         /* Here we change it back. */
-        if (keysym == XK_ISO_Left_Tab)
+        if (keysym == XK_ISO_Left_Tab && !(e.state & ControlMask))
         {
             bufW[0] = 0x09;
             ret = 1;