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/testrelative.c

@@ -0,0 +1,100 @@
+/*
+  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely.
+*/
+
+/* Simple program:  Test relative mouse motion */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "SDL_test_common.h"
+
+
+static SDLTest_CommonState *state;
+static SDL_Rect rect;
+
+static void
+DrawRects(SDL_Renderer * renderer)
+{
+    SDL_SetRenderDrawColor(renderer, 255, 127, 0, 255);
+    SDL_RenderFillRect(renderer,&rect);
+}
+
+int
+main(int argc, char *argv[])
+{
+    int i, done;
+    SDL_Event event;
+
+
+    /* Initialize test framework */
+    state = SDLTest_CommonCreateState(argv, SDL_INIT_VIDEO);
+    if (!state) {
+        return 1;
+    }
+    for (i = 1; i < argc;i++) {
+        SDLTest_CommonArg(state, i);
+    }
+    if (!SDLTest_CommonInit(state)) {
+        return 2;
+    }
+
+    /* Create the windows and initialize the renderers */
+    for (i = 0; i < state->num_windows; ++i) {
+        SDL_Renderer *renderer = state->renderers[i];
+        SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE);
+        SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
+        SDL_RenderClear(renderer);
+    }
+
+    srand((unsigned int)time(NULL));
+    if(SDL_SetRelativeMouseMode(SDL_TRUE) < 0) {
+        return 3;
+    };
+
+    rect.x = DEFAULT_WINDOW_WIDTH / 2;
+    rect.y = DEFAULT_WINDOW_HEIGHT / 2;
+    rect.w = 10;
+    rect.h = 10;
+    /* Main render loop */
+    done = 0;
+    while (!done) {
+        /* Check for events */
+        while (SDL_PollEvent(&event)) {
+            SDLTest_CommonEvent(state, &event, &done);
+            switch(event.type) {
+                case SDL_MOUSEMOTION:
+                {
+                    /*printf("mouse motion ABS x %d y %d REL x %d y %d\n",event.motion.x,event.motion.y,event.motion.xrel,event.motion.yrel);*/
+                    rect.x += event.motion.xrel;
+                    rect.y += event.motion.yrel;
+
+                }
+                break;
+            }
+        }
+        for (i = 0; i < state->num_windows; ++i) {
+            SDL_Renderer *renderer = state->renderers[i];
+            SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
+            SDL_RenderClear(renderer);
+
+            DrawRects(renderer);
+
+            SDL_RenderPresent(renderer);
+        }
+    }
+
+    SDLTest_CommonQuit(state);
+    return 0;
+}
+
+/* vi: set ts=4 sw=4 expandtab: */