Simplify make_range by using move semantics

Move the iterators into the range the same way the range's ctor moves
them into the members.

Also remove some redundant top level parens in the return statement.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205993 91177308-0d34-0410-b5e6-96231b3b80d8