Merging r221832:

Merging r221832:

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r221832 | richard-llvm | 2014-11-12 18:38:38 -0500 (Wed, 12 Nov 2014) | 5 lines

PR19372: Keep checking template arguments after we see an argument pack
expansion into a parameter pack; we know that we're still filling in that
parameter's arguments. Previously, if we hit this case for an alias template,
we'd try to substitute using non-canonical template arguments.

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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_35@223719 91177308-0d34-0410-b5e6-96231b3b80d8