Do not lock modifiers if sliding a key

This unconditionally removes all pointers (touches) pressing modifiers
which are not already locked, avoiding that the (currently) latched
modifier will be locked aventually.

This can be verfified while sliding the space bar to move the cursor
left or right.

Closes #319.

srcs/juloo.keyboard2/Pointers.java

@@ -113,6 +113,7 @@ public final class Pointers implements Handler.Callback
       return;
     if (ptr.sliding)
     {
+      clearLatched();
       onTouchUp_sliding(ptr);
       return;
     }