pkgsrc-wip/ghc710

This package was forked from wip/ghc because wip/ghc doesn't build.

The idea with this package is to use lang/ghc7 (which is a ghc 7.6.3) to build
wip/ghc710 (which is ghc 7.10.3) and then use wip/ghc710 to build wip/ghc8
(which is ghc 8.0.1) as ghc version 7.8 or later is required in order to build ghc 8.0.1.

We already have lang/ghc7 in pkgsrc that manages to bootstrap and build. We use it to build
ghc 7.10.3, which will be used to build ghc 8.0.1