Improvements from Alfred:

- Added new SDL_HINT_ALLOW_TOPMOST hint, when set to "0" then never set the topmost bit on a window. Useful when debugging fullscreen issues.
- fixed crash in windows joystick scanning if we failed to load the xinput dll
- added support for SDL_WINDOW_FULLSCREEN_DESKTOP under windows
- synthesize relative mouse movements if directinput fails to send relative moves, happens under virtual box.

include/SDL_hints.h

@@ -204,6 +204,18 @@ extern "C" {
 #define SDL_HINT_GAMECONTROLLERCONFIG "SDL_GAMECONTROLLERCONFIG"
 
 
+/**
+ *  \brief If set to 0 then never set the top most bit on a SDL Window, even if the video mode expects it.
+ *		This is a debugging aid for developers and not expected to be used by end users. The default is "1"
+ *
+ *  This variable can be set to the following values:
+ *    "0"       - don't allow topmost
+ *    "1"       - allow topmost
+ */
+#define SDL_HINT_ALLOW_TOPMOST "SDL_ALLOW_TOPMOST"
+
+
+
 /**
  *  \brief  An enumeration of hint priorities
  */