Update SDL to 2.0.7

libs/SDL2/src/SDL_hints.c

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2017 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
@@ -122,7 +122,7 @@ SDL_bool
 SDL_GetHintBoolean(const char *name, SDL_bool default_value)
 {
     const char *hint = SDL_GetHint(name);
-    if (!hint) {
+    if (!hint || !*hint) {
         return default_value;
     }
     if (*hint == '0' || SDL_strcasecmp(hint, "false") == 0) {