Sema: Reject templates in all extern "C" contexts.

Otherwise we'd accept them if the LinkageDecl was not the direct
parent DeclContext. PR17968.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200641 91177308-0d34-0410-b5e6-96231b3b80d8
clang/lib/ASTMatchers/Dynamic/CMakeLists.txt: redundant

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200642 91177308-0d34-0410-b5e6-96231b3b80d8
clang/CMakeLists.txt: Untabify.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200643 91177308-0d34-0410-b5e6-96231b3b80d8