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.

build-scripts/updaterev.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+#
+# Generate a header file with the current source revision
+
+outdir=`pwd`
+cd `dirname $0`
+srcdir=..
+header=$outdir/include/SDL_revision.h
+
+rev=`sh showrev.sh 2>/dev/null`
+if [ "$rev" != "" -a "$rev" != "hg-0:baadf00d" ]; then
+    revnum=`echo $rev | sed 's,hg-\([0-9]*\).*,\1,'`
+    echo "#define SDL_REVISION \"$rev\"" >"$header.new"
+    echo "#define SDL_REVISION_NUMBER $revnum" >>"$header.new"
+    if diff $header $header.new >/dev/null 2>&1; then
+        rm "$header.new"
+    else
+        mv "$header.new" "$header"
+    fi
+fi