Make the User::value_op_iterator a random access iterator. I had written
this code ages ago and lost track of it. Seems worth doing though --
this thing can get called from places that would benefit from knowing
that std::distance is O(1). Also add a very fledgeling unittest for
Users and make sure various aspects of this seem to work reasonably.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206453 91177308-0d34-0410-b5e6-96231b3b80d8
[LCG] Move the call graph node class into the graph class's definition.
This will become necessary to build up the SCC iterators and SCC
definitions. Moving it now so that subsequent diffs are incremental.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206454 91177308-0d34-0410-b5e6-96231b3b80d8
[LCG] Remove a dead declaration. This stopped being used when I switched
to a more normal move operation on the graph itself. The definition
already got removed, but I missed the declaration.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206455 91177308-0d34-0410-b5e6-96231b3b80d8