Parser no longer checks for a declared constructor when handling a
using declaration in order to correct the name as it won't find
implicitly declared constructors. Now it checks that a using
declaration is for something that looks like a constructor instead
by checking the immediate base classes for allowed constructors.
Internal using name no longer contains template parameters.
Fixes symbol table lookup for non-instantiated template constructor.
Builds on previous few commits where the internal name no longer
contains the template parameters for constructors and destructors.
William S Fulton