The "future-dev" branch of MSOpenTech's ANGLE/WinRT repository (at
https://github.com/msopentech/angle) includes support for Windows Phone 8.1.
This change allows it to be used in conjunction with SDL's OpenGL functions.
A negative periodic magnitude doesn't exist in Windows' and MacOS' FF APIs
The periodic magnitude parameter of the SDL Haptic API is based on the Linux
FF API, so it means they are not directly compatible:
'dwMagnitude' is a 'DWORD', which is unsigned.
Fixes Bugzilla #2701.
since the window system doesn't do it for us like other platforms.
This prevents sticky keys and missed keys when going in and out
of focus, for example Alt would appear to stick if switching away
from an SDL app with Alt-Tab and had to be pressed again.
CR: Sam
