ANGLE: Disable support for shared handles in warp mode on Windows < 8

Shared handles are not supported on Windows 7 and below. If the
according flag is set CreateTexture2D will fail with E_OUTOFMEMORY. The
check already happens with newer ANGLE versions, which we use in 5.7
but has to happen here as well. Otherwise Qt applications running on
Windows 7 and below will crash at startup.

Change-Id: I8f539f16dce298611fb1ec7b2f6804d4a04d04e0
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>