This change makes sure the memset template is not
used with classes that contain virtual members.

Bug: b/152253831
Change-Id: I07d4777f33a9bd55c8f99d8b50a80c13df5d5805
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/49648
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Jari Komppa <jari@siru.fi>