Backport hhvm-9999 to hhvm-3.0.1 to fix the build.
Update hhvm-9999. Improve folly handling, and drop 32bit compatibility patch foro mysql libs
Drop ebuilds for HHVM versions prior to 3.0.1
Drop two unused patches from the hhvm ebuilds
Remove all gcc files as 4.9 has no officially made it into portage
Simplify hhvm-9999 folly logic