Proposal: Remove Data.HashTable from base

[Ian Lynagh]

Hi all,

Historically, Data.HashTable has been in base because Data.Typeable used
it, but that is no longer the case.

I propose that we:
* Mark it as deprecated in the base that comes with GHC 7.6.
* Remove it from the base that comes with GHC 7.8.

Rationale:
* Historically there have been performance problems with it, and we have
  been recommending people not to use it. I'm not sure if that's still
  the case or not.
* If it is still useful then it would fit better in the containers
  package. However, as there is no reason that it needs to be tied to
  the GHC release schedule etc, it would be even better to put it in
  another package.

In GHC, deSugar/Coverage.lhs does use the module, but only for
hashString. We could put this elsewhere in base, but I think it would be
better just to copy the definition into the GHC source.


Suggested discussion deadline: Fri 29 June 2012.


Thanks
Ian