If an instantiation of a template is required to be a complete type, check

If an instantiation of a template is required to be a complete type, check
whether the definition of the template is visible rather than checking whether
the instantiated definition happens to be in an imported module.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@208150 91177308-0d34-0410-b5e6-96231b3b80d8