Interface blocks can now properly return their size from
TType::getElementSize() or TType::elementRegisterCount().

Change-Id: Ief69163088839784cf347160bb49fd64f1a2a395
Reviewed-on: https://swiftshader-review.googlesource.com/3584Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>