WinRT: Got OpenGL ES 2 working with the latest version of ANGLE/WinRT.

SDL/WinRT did have support for OpenGL ES 2 via an older version of ANGLE/WinRT,
however its API changed a few months ago, and SDL/WinRT would crash when trying
to use it.  It would also occasionally crash when using the older version.

This changeset should make SDL/WinRT work with the latest version, as
available via MS Open Tech's git repository of it at
https://github.com/msopentech/angle

Older versions of ANGLE/WinRT (from either https://github.com/stammen/angleproject
or https://bitbucket.org/DavidLudwig/angleproject) will need to be updated to
MS Open Tech's latest version.

--HG--
extra : rebase_source : 4dbab8a703aaa1d9820bd45297ebbb1ccc895883