Xi: don't memcpy the KeyClassRec from SD to MD. #16167

Most of its component get copied during CopyKeyClass anyway.
The ones that aren't:
  postdown - never changed for virtual devices anyway.
  down - shouldn't change that without sending events.

memcpy'ing the struct also copied mapWidth, which means we didn't realloc
during SetKeySymsMap lateron, overwriting the memory assigned to us.

X.Org Bug 16167 <http://bugs.freedesktop.org/show_bug.cgi?id=16167>

Xi/exevents.c

@@ -527,8 +527,6 @@ DeepCopyDeviceClasses(DeviceIntPtr from, DeviceIntPtr to)
         oldXkbInfo      = to->key->xkbInfo;
 #endif
 
-        memcpy(to->key, from->key, sizeof(KeyClassRec));
-
         if (!oldMap) /* newly created key struct */
         {
             int bytes = (to->key->curKeySyms.maxKeyCode -