Summary:
3.4.6 [basic.lookup.udir] paragraph 1:
In a using-directive or namespace-alias-definition, during the lookup for a namespace-name or for a name in a nested-name-specifier, only namespace names are considered.

Reviewers: rsmith, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D30848

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@298126 91177308-0d34-0410-b5e6-96231b3b80d8