Add support for mangling ObjC protocol conformances in MS ABI as if they are COM interfaces. By diverging from the itanium mangling of objc_protocol prefixed names, this approach allows for a semi-reasonable, albeit of questionable sanity, undecoration via existing tooling. There is also the possibility of adding an extension and taking part of the namespace to add the conformance via the L and Z "modifiers", but the existing tooling would not be able to properly undecorated the symbol even though incidentally undname currently produces something legible while wine's implementation is not able to cope with the extension.
This allows for the disambiguation of overloads where the parameter differs only in the protocol conformance of the ObjC type, e.g.
@protocol P; void f(std::vector<id>); void f(std::vector<id<P>>);
which clang would previously fail due to the mangling being identical as the protocol conformance was ignored.