For example:
    template <typename ::foo::bar>...

Done by: Roberto Raggi
Reviewed-by: erikv

For example,
  template <template <typename> class X> struct foo {};

Reviewed-by: erikv

The check should be done in the semantic phase.

Reviewed-by: Roberto Raggi

This reverts commit 2a59d2ae.

This reverts commit f4163b8b.