This change has also been tested as buildable + runnable on Win32 + MSVC 2015,
2013, 2012, and 2010. It may fix similar build errors (in XInput code) that
are appearing in MingW builds (on buildbot).
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
