Call RequireCompleteType when performing ADL even if the type is already
complete. We hook into this check from a couple of other places (modules,
debug info) so it's not OK to elide the check if the type was already
complete.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203978 91177308-0d34-0410-b5e6-96231b3b80d8