Make ExtVMFace polymorphic to give JIT hope for working
Another round of fixing ExtVM interface
Remove dead code
Add virtual destructor for ExtVMFace, make the class non-copyable.
Make ExtVMFace::getCode non-virtual
Make overridden methods in ExtVM final - maybe some optimization possibilities?
Add virtual specifier to overridden methods in FakeVM
Drop universal initializer in some places
Merge pull request #406 from imapp-pl/pr-changes

ExtVMFace pylimorphic changes