PR31469: Don't add friend template class decls to redecl chain in dependent contexts.

PR31469: Don't add friend template class decls to redecl chain in dependent contexts.

Fixes a crash in modules where the template class decl becomes the most recent
decl in the redeclaration chain and forcing the template instantiator try to
instantiate the friend declaration, rather than the template definition.

In practice, A::list<int> produces a TemplateSpecializationType
A::__1::list<int, allocator<type-parameter-0-0> >' failing to replace to
subsitute the default argument to allocator<int>.

Kudos Richard Smith (D28399).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291753 91177308-0d34-0410-b5e6-96231b3b80d8