Updates SDL to version 2.0.4, which makes it compatible with VS2015.

Engine/lib/sdl/src/filesystem/android/SDL_sysfilesystem.c

@@ -0,0 +1,62 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2016 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_internal.h"
+
+#ifdef SDL_FILESYSTEM_ANDROID
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+/* System dependent filesystem routines                                */
+
+#include <unistd.h>
+#include <errno.h>
+
+#include "SDL_error.h"
+#include "SDL_filesystem.h"
+#include "SDL_system.h"
+
+
+char *
+SDL_GetBasePath(void)
+{
+    /* The current working directory is / on Android */
+    return NULL;
+}
+
+char *
+SDL_GetPrefPath(const char *org, const char *app)
+{
+    const char *path = SDL_AndroidGetInternalStoragePath();
+    if (path) {
+        size_t pathlen = SDL_strlen(path)+2;
+        char *fullpath = (char *)SDL_malloc(pathlen);
+        if (!fullpath) {
+            SDL_OutOfMemory();
+            return NULL;
+        }
+        SDL_snprintf(fullpath, pathlen, "%s/", path);
+        return fullpath;
+    }
+    return NULL;
+}
+
+#endif /* SDL_FILESYSTEM_ANDROID */
+
+/* vi: set ts=4 sw=4 expandtab: */