Handling of implicit ctor parameters in MS and Itanium ABI

[tritao]

So while looking through Clang MS ABI codegen code I noticed some ctors can have an extra implicit parameter which we do not handle.

See MicrosoftCXXABI::addImplicitConstructorArgs.

Additionally the parameter position changes depending if the method is variadic or not.

  // Add the 'most_derived' argument second if we are variadic or last if not.

Similar thing for Itanium ABI as can be seen on Clang's Itanium codegen code.

  // Insert the implicit 'vtt' argument as the second argument.

[ddobrev]

The best way to fix this is by reading the implicit parameters from Clang in Parser::WalkFunction (the part at the end about the code gen info). It might also be related to https://github.com/mono/CppSharp/issues/1450.

[tritao]

Its not related, this is just for some type of constructors.