[Agda] 64-bit agda

[James Chapman]

I built the release version of agda with the macports haskell platform
and this does give me a 64-bit agda by default. It can use more than
4GB or memory. But, as this version doesn't have the dramatic
improvements in performance for dependent records this isn't
necessarily an advantage!

> Darin introduced a dependency on recent versions of Cabal in his work on
> Cabal support for Agda.

Is it possible to turn this off temporarily? I tried simply relaxing
the version constrains in the .cabal files but this happened:

[171 of 199] Compiling Agda.Packaging.Database (
src/full/Agda/Packaging/Database.hs,
dist/build/Agda/Packaging/Database.o )

src/full/Agda/Packaging/Database.hs:25:4:
    Module `System.IO' does not export `hSetEncoding'

src/full/Agda/Packaging/Database.hs:27:4:
    Module `System.IO' does not export `utf8'

src/full/Agda/Packaging/Database.hs:40:6:
    Module
    `Distribution.InstalledPackageInfo'
    does not export
    `installedPackageId'
cabal: Error: some packages failed to install:
Agda-2.2.7 failed during the building phase. The exception was:
exit: ExitFailure 1

It would help if I knew what I was doing...

Regards,

James