Remove obsolete Agda-executable package; the compiler is not part of 'Agda'.
HTTP-4000.2.13: jailbreak to fix build with latest version of conduit

https://github.com/haskell/HTTP/issues/61
https://github.com/NixOS/nixpkgs/issues/2495
haskell-HTTP-4000.2.13: disable test suite to fix the build

https://github.com/haskell/HTTP/issues/60