Port visible bell to Android

Port visible bell to Android

* java/org/gnu/emacs/EmacsDrawRectangle.java (perform): Ignore
GC_INVERT.

* java/org/gnu/emacs/EmacsFillRectangle.java
(EmacsFillRectangle) <invertFilter>: New variable.
(perform): If the transfer mode is invert, copy the source
to itself with invertFilter as the color filter.

* java/org/gnu/emacs/EmacsGC.java (EmacsGC) <xorAlu, srcInAlu>:
Delete now-redundant ALUs.
(markDirty): Cease updating the paint's transfermode.

* java/org/gnu/emacs/EmacsSafThread.java (openDocument1): Fix
typo in documentation.

* src/android.c (android_blit_xor): Delete unused function.
(android_copy_area): Remove calls to unused blit functions.

* src/androidgui.h (enum android_gc_function): Rename XOR to
INVERT.

* src/androidterm.c (android_flash): Replace with GXinvert.