[jhc] darcs patch: code cleanups, used located in hstype, u... (and 4 more)

Wed Feb 1 05:20:53 PST 2012 John Meacham * code cleanups, used located in hstype, use packedstring for filename. Thu Feb 2 20:17:57 PST 2012 John Meacham * turn WarnType into a real algebraic data type. Sat Feb 4 14:07:32 PST 2012 John Meacham * switch kind inference to use the unified warnings mechanism, switch class declarations to use a HsClassHead Sat Feb 4 16:02:03 PST 2012 John Meacham * improve kind checking, kind check instance heads before typechecking pass, switch HsInstDecl to use the HsClassHead Sat Feb 4 16:30:34 PST 2012 John Meacham * add ghc typecheck failure tests