Fixes #2022, do not resume on Android when surfaceChanged

If the app is in landscape mode and the user presses the power button, a pause
is followed immediately by a surfaceChanged event because the lock screen
is shown in portrait mode. This triggers a "false" resume.
So, we just pause and resume following the onWindowFocusChanged events.

Also, wait for SDL_APP_WILLENTERBACKGROUND and SDL_APP_DIDENTERBACKGROUND before
blocking the event pump.

test/COPYING

@@ -0,0 +1,8 @@
+
+The test programs in this directory tree are for demonstrating and
+testing the functionality of the SDL library, and are placed in the
+public domain.
+
+October 28, 1997
+--
+	Sam Lantinga				(slouken@libsdl.org)