Also remove default constructors and unused members.

Bug chromium:801648

Change-Id: I822ca1e1569708ca661796ee9252bae68a0a284a
Reviewed-on: https://swiftshader-review.googlesource.com/16948Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>