[RFC] widl: Add option to generate classfactory

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=44187

Your paranoid android.


=== debian9 (build log) ===

Makefile:263: recipe for target 'uiribbon_classes_f.o' failed
Makefile:8635: recipe for target 'dlls/uiribbon' failed
Task: The win32 build failed

=== debian9 (build log) ===

Makefile:262: recipe for target 'uiribbon_classes_f.o' failed
Makefile:8360: recipe for target 'dlls/uiribbon' failed
Task: The wow64 build failed