Make C++11 status page more consistent: we mark entries as "done" if we
implement correct functionality, even if it's not optimal. On this basis, mark
"data dependency ordering" as done. Add footnotes for cases where our
implementation is known to be suboptimal.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176891 91177308-0d34-0410-b5e6-96231b3b80d8