Avert race condition between window attachment and buffer swap

Avert race condition between window attachment and buffer swap

* java/org/gnu/emacs/EmacsView.java (swapBuffers): Synchronize
such that code cannot execute between the bitmap's being loaded
and being transferred to surfaceView.
(onDetachedFromWindow): Recycle bitmap after the surface view is
reset.

* java/org/gnu/emacs/EmacsWindow.java (recreateActivity):

* src/android.c (android_init_emacs_window)
(android_recreate_activity):

* src/androidfns.c (Fandroid_recreate_activity)
(syms_of_androidfns): New functions for debugging window
attachment.

* src/androidgui.h: Update prototypes.