Frontend: Don't free the CompilerInstance or FrontendActions when running under

-disable-free. Among other things, this fixes freeing of the LLVM module on
exit.
 - Note that this means we are disable-free'ing of a lot more stuff than we used to -- this should flush out bugs in anything left that is trying to do real work in its destructor. I did a mini-audit but '::~' is not totally uncommon.

llvm-svn: 99258