Eliminated the CompletedNodes argument to the cloneReachable* methods. This

Eliminated the CompletedNodes argument to the cloneReachable* methods.  This
map was only used to implement a marginal GlobalsGraph optimization, and it
actually slows the analysis down (due to the overhead of keeping it), so just
eliminate it entirely.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10955 91177308-0d34-0410-b5e6-96231b3b80d8