CWG1819 Acceptable scopes for definition of partial specialization
CWG1838 Definition via unqualified-id and using-declaration

Also fixes CWG1021.
CWG1848 Parenthesized constructor and destructor declarators
CWG1858 Comparing pointers to union members
CWG1865 Pointer arithmetic and multi-level qualification conversions
CWG1866 Initializing variant members with non-trivial destructors
CWG1870 Contradictory wording about definitions vs explicit specialization/instantiation
CWG1874 Type vs non-type template parameters with class keyword