[FEAT]: Missing msssrs.cpp in SDK source

[QianNangong]

Description

It may be the only file I found missing in SDK source.

Additional Information

No response

[Veryzon]

Yes. I also noticed that while generating a Visual Studio solution for it. Appearently, that file is also missing in other SDKs (6 and 7) to be released soon. This codebase seem to be a merge between the version 9.3b and 9.3c. Maybe an update. Anyway, if we could not fix it, I think we may reverse engine the compiled libraries and reconstruct the SRS code unit.