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.

src/SDL_error_c.h

@@ -0,0 +1,64 @@
+/*
+  Simple DirectMedia Layer
+  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, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "SDL_config.h"
+
+/* This file defines a structure that carries language-independent
+   error messages
+*/
+
+#ifndef _SDL_error_c_h
+#define _SDL_error_c_h
+
+#define ERR_MAX_STRLEN  128
+#define ERR_MAX_ARGS    5
+
+typedef struct SDL_error
+{
+    /* This is a numeric value corresponding to the current error */
+    int error;
+
+    /* This is a key used to index into a language hashtable containing
+       internationalized versions of the SDL error messages.  If the key
+       is not in the hashtable, or no hashtable is available, the key is
+       used directly as an error message format string.
+     */
+    char key[ERR_MAX_STRLEN];
+
+    /* These are the arguments for the error functions */
+    int argc;
+    union
+    {
+        void *value_ptr;
+#if 0                           /* What is a character anyway?  (UNICODE issues) */
+        unsigned char value_c;
+#endif
+        int value_i;
+        double value_f;
+        char buf[ERR_MAX_STRLEN];
+    } args[ERR_MAX_ARGS];
+} SDL_error;
+
+/* Defined in SDL_thread.c */
+extern SDL_error *SDL_GetErrBuf(void);
+
+#endif /* _SDL_error_c_h */
+
+/* vi: set ts=4 sw=4 expandtab: */