gcc: update 4.9.1 bottle.

Closes #31911.
torsocks v2.0.0

Closes #31895.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
Structure the build process so that we don't need an at_exit hook
ipv6toolkit v1.5.3

Closes #31635.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
ghc 7.8.3
cabal-install: Anticipate and fix GHC 7.8 bug.
ghc: bump bundled Cabal version to 1.18.1.4.

Otherwise, attempting to `brew install cabal-install` will still fail,
despite forcing cabal-install's bootstrap script to use Cabal 1.20.0.2
instead of Cabal 1.20.0.0.
cabal-install: update 1.20.0.3 bottle.
ghc: update 7.8.3 bottle.