Fix use of operator comma in is_permutation and delete comma operator for test iterators.

The comma operators in the test iterators give better error messages when they
are deleted as opposed to not defined. Delete these functions when possible.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@220715 91177308-0d34-0410-b5e6-96231b3b80d8