feature is set, then the features in the implied list should be set also.
The opposite is also enforced: if a feature in the implied list isn't set,
then the feature that owns that implies list shouldn't be set either.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36756 91177308-0d34-0410-b5e6-96231b3b80d8