Improve name mangling
- Make MSVC toolset mangling optional. These days, MSVC is very good at backwards compatibility so the toolset information is not that important.
- Fix MSVC runtime library handling. It seems that the whole runtime library related logic should be under MSVC condition.
- Make MSVC runtime library mangling optional. This might make using different compilers a bit easier in cases where their C++ ABI does not have to match, e.g. for dynamically loaded plugins using C ABI.
Edited by Innokentiy Alaytsev