Remove GHC.Err import from Data.Maybe

[Neil Mitchell]

Hi,

I noticed that Data.List uses "error" normally, but Data.Maybe
explicitly imports it from GHC.Err. Is there a reason for this?
Removing the import GHC.Err line still appears to work.

This caused me issues with circular modules and recursive boot files,
in various mixtures. It's not a fatal issue, but since it seems to be
a cleanup, it might be worth doing.

Thanks

Neil