Windows clang requires that intrinsics be properly declared
through intrin.h, otherwise, intrinsics were getting
manually declared through a pragma instruction from winnt.h
and clang returned an error.

Change-Id: Iddfa4e3d6c76388e986dc445e40fd05359c2763c
Reviewed-on: https://swiftshader-review.googlesource.com/7050Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>