Summary:
This eliminates the boilerplate implementation of the iterator interface in
mapped_iterator.
This patch also adds unit tests that verify that the mapped function is applied
by operator* and operator->, and that references returned by the map function
are returned via operator*.
Reviewers: dblaikie, chandlerc
Subscribers: llvm-commits, mgorny
Differential Revision: https://reviews.llvm.org/D39855
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317902 91177308-0d34-0410-b5e6-96231b3b80d8
9e7ee78426