Update Android port

Update Android port

* src/android.c (android_select, android_check_query)
(android_check_query_urgent, android_answer_query)
(android_answer_query_spin, android_begin_query, android_end_query)
(android_run_in_emacs_thread): Use finer grained memory
synchronization semantics.
* src/androidterm.c (android_get_selection): Use the current
selection, not its value at the time of the last redisplay.
* src/keyboard.c (handle_input_available_signal): Place memory
barrier.