Problem: Skipping over an expression when not evaluating it does not work
properly for dict members.
Solution: Skip over unrecognized expression. (ZyX)
Problem: It is possible to add replace builtin functions by calling
extend() on g:.
Solution: Add a flag to a dict to indicate it is a scope. Check for
existing functions. (ZyX)
Problem: Calling a function through a funcref, where the function deletes
the funcref, leads to an invalid memory access.
Solution: Make a copy of the function name. (Lech Lorens)
