[ASTImporter] Added visibility context check for TypedefNameDecl.

[ASTImporter] Added visibility context check for TypedefNameDecl.

Summary:
ASTImporter makes now difference between typedefs and type aliases
with same name in different translation units
if these are not visible outside.

Reviewers: martong, a.sidorin, shafik, a_sidorin

Reviewed By: martong, shafik

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64480

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@370903 91177308-0d34-0410-b5e6-96231b3b80d8