Fix conflicting dns deps and one test suite, disable network tests for haeredes

The current ebuild for dev-haskell/dns has RESTRICT="test" due to the doctests crashing, but this is a symptom of a larger problem: the network and network-bytestring deps conflict, so you can't e.g. load the library in ghci without hiding network-bytestring.

I've manually set the deps to those from the GHC >= 7 clause in the cabal file -- this avoids the conflict which arises when using the GHC-6.x deps (hackport's default).

I've also enabled one of the dns test suites -- the one that doesn't access the network. In the same vain, I've disabled the doctests for haeredes which access the network and might annoy people.