[analyzer] Make CloneDetector consider template arguments.

For example, code samples `isa<Stmt>(S)' and `isa<Expr>(S)'
are no longer considered to be clones.

Patch by Raphael Isemann!

Differential Revision: https://reviews.llvm.org/D23555


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@279366 91177308-0d34-0410-b5e6-96231b3b80d8