[msvc] Fixed missing semi-colon.
Removed some dead code.
[msvc] Fixed empty struct declaration (it's not valid C according to MSVC).
[msvc] Updated project files.
[msvc] Fixed heap problems at runtime when calling free().

Due to an incompatibility in the project files and DLL API setup code, we were importing locally defined symbols as DLL. This manifested as a debug heap dialog in VS caused by allocating and freeing memory between two Windows modules (which have their own memory heap).

Fix this by simplifying the DLL defines in MSVC, we are relying on .def files to manually specify the exports anyway.
[driver] Fixed outdated URL in help message.
[mcs] Add support for __refvalue passed as a reference
[mcs] At least one of nameof methodgroup argument candidates needs to be accessible
[mcs] Improve extension methods error reporting