Removal of older llvm/clang ports

[Jeremy Huddleston Sequoia]

We're approaching the release of llvm-3.6 and will add another llvm port to track 3.7 when 3.6 branches some time in the next month.  At that point, we'd have 9 different versions of llvm available in MacPorts (2.9 through 3.7), which is a bit more than I think is necessary.

I'd like to obsolete the following ports (and all their subports) next week and want to know if there are any objections to this:
llvm-2.9
llvm-3.0
llvm-3.1
llvm-3.2
dragonegg-3.0
dragonegg-3.1
dragonegg-3.2

I intend to leave llvm-3.3 and llvm-3.4 around for quite some time as they are the last two versions that will compile with libstdc++ and are thus needed to bootstrap libc++ on pre-Lion systems.  They are also the last two releases for which the dragonegg gcc backend plugin was supported.

Note that these ports are already unsupported on Mavericks and Yosemite, so this should hopefully not impact too many people, but please let me know if there are any concerns.

Thanks,
Jeremy