[openssl-project] Is Mac a supported platform?

[Salz, Rich]

>    Regarding the original question, it's "supported" insofar that we have
    osx among the Travis builds (at least usually...  there have been
    times when the osx backlog has been so great that we've temporarly
    disabled it).
  
So maybe I should just create a PR to update INSTALL with the Mac recipe?