Implement more Android text editing controls

Implement more Android text editing controls

* lisp/term/android-win.el (android-deactivate-mark-command):
New command.
(select-all, start-selecting-text, stop-selecting-text): Arrange
for commands manipulating the region to be executed when these
keys are registered.

* src/android.c (android_get_keysym_name): Return the keysym
name of each of the new keysyms introduced.

* src/androidterm.c (performContextMenuAction): Save special
keysyms into key events for the selectAll, startSelectingText
and stopSelectingText actions.