Updates to support base-4.7 from GHC 7.7-2013116

[argiopetech]

Adds updates to support the new Typeable in base-4.7.0.0.
Switches from MonadCatchIO-mtl to MonadCatchIO-transformers (latter is supported in 7.8)
Adds explicit (Functor m) constraint on tryCGI (this is the only source change not in #if MIN_VERSION_base(4,7,0) blocks).

[andersk]

Thanks. I’m still not sure what should happen to the MonadCatchIO dependency, though. The Haskell Platform guys didn’t accept MonadCatchIO-mtl into the platform, and so HP is stuck on the 3001.1.7 branch (#1). It turns out MonadCatchIO also has various semantic problems. I’m not sure if MonadCatchIO-transformers is going to do any better on either point. Last I heard, the new thing was going to be ekmett’s exceptions (even though I think its semantics are not quite ideal either), but I haven’t seen it confirmed that exceptions will be okay for HP. Until that’s sorted out, I don’t want to release many different versions forcing users to switch exception libraries.

[argiopetech]

Optimally, we remove the dependency altogether. MonadCatchIO-foo is in the process of being deprecated as base-4.7 finally removes block and unblock from Control.Exception. Rewriting either with exceptions or with Control.Exception.mask would be preferable.

I'll look into a patch that implements this later.