almost all clang & llvm versions updated today

[Ken Cunningham]

Apologies,

Due to a need to reinstitute @rpath-based dylib naming, to fix several bugs that showed up primarily when debugging with clang, all the clang/llvm/lldb versions from 3.9 up were revbumped today.

If you wait a while for the buildbots to build these for you, your "upgrade outdated" will be much less painful.

You can check the builtbot's progress by looking, for example, on <https://packages.macports.org/llvm-8.0/> to see if your particular needs have been met before the update.

Ken