Fixing 9808 on the Motif side, too.

widget/src/motif/nsXtEventHandler.cpp

@@ -41,6 +41,7 @@ struct nsKeyConverter nsKeycodes[] = {
   { NS_VK_CANCEL,     XK_Cancel },
   { NS_VK_BACK,       XK_BackSpace },
   { NS_VK_TAB,        XK_Tab },
+  { NS_VK_TAB,        XK_ISO_Left_Tab },
   { NS_VK_CLEAR,      XK_Clear },
   { NS_VK_RETURN,     XK_Return },
   { NS_VK_SHIFT,      XK_Shift_L },