Fix Bug 879 - Threads deadlock in native keyboardfocus calls made form multiple threads; Fix Bug 892: Reduce Focus Hopping

Since we manage focus key traversal ourselves w/o requiring the AWT
component to have the focus[1],
we simply can drop requesting the focus for 'focus hopping' NEWT -> AWT -> NEWT[2].

Further more, 'MenuSelectionManager.defaultManager().clearSelectedPath()'
must be performed on AWT-EDT w/o blocking. Otherwise it may perform blocking tasks on AWT-EDT.

[1] Commit cb7118fc875b6722803e4b11d5681671962a8d3a
introduced function to query the next or previous 'to be focused' component:
   AWTMisc.getNextFocus(..) .. etc.

[2] Focus hopping is also addressed in Bug 892