Run-time check to verify the Cabal version that cabal-install was built with

[creswick]

cabal-dev requires that the invoked cabal-install was built with Cabal >= 1.8.0.6, but this is a run-time check, so it can not be sensibly checked during the cabal-dev build.

This has proven to be an issue, since it is difficult to diagnose and many people run cabal-install with slightly older versions of Cabal.

[creswick]

This bug now deserves clarification:

cabal-dev does now do run-time checks to determine file parsing capabilities, but it does not yet warn if you are running cabal-dev with a version of cabal-install < 0.8.2 or if cabal-install was built with a cabal < 1.8.0.6. (The cabal-install version is checked at compile time, which is a pretty good indication, but not sufficient.)