Remove 'check-dg', a wrapper around 'check-local-dg' which was just
nuked.

Add a comment that the 'check-lit' rule is really just a legacy of
having two test runners.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159310 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed