Don't build broken Haskell packages on Hydra.

These packages don't compile:

 - cabal-delete
 - cabal-file-th
 - categories
 - cmdtheline
 - codec-image-devil
 - concurrent-extra
 - cryptol 1.8.x
 - data-lens
 - pakcs

These packages depend on some of the packages listed before:

 - data-lens-template
 - purescript