Log Message:
lang/clang: USE_TOOLS+= pod2man pod2html, fix DragonFly

For some reason, LLVM is using autoconf files from 2003 which is before
DragonFly even existed.  I submitted a bug report #12944 at llvm.org's
bugzilla to request they use versions from 2012.

Also, installation fails at document generation without some extra tools.
No need to revbump, either built or it didn't without these packages.