Summary:
* Updated the documentation
* Added a test for >2 arguments
* Added a check for the lexical concatenation
* Made the existing test a bit stricter.
Reviewers: t.p.northover
Reviewed By: t.p.northover
Subscribers: t.p.northover, llvm-commits
Differential Revision: http://reviews.llvm.org/D3485
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207865 91177308-0d34-0410-b5e6-96231b3b80d8