[ASTImporter] Use InjectedClassNameType at import of templated record.

Summary:
At import of a record describing a template set its type to
InjectedClassNameType (instead of RecordType).

Reviewers: a.sidorin, martong, r.stahl

Reviewed By: a.sidorin, martong, r.stahl

Subscribers: a_sidorin, rnkovacs, martong, cfe-commits

Differential Revision: https://reviews.llvm.org/D47450

Patch by Balazs Keri!

llvm-svn: 335600