[project @ 2001-12-07 07:37:43 by sof]
Tidyup - previous instance-decl commit fell a bit short:
* RnEnv.lookupInstDeclBndr unceremoniously fell over when passed
an out-of-scope class name.
* the AvailEnv carried around didn't common up type/class info
(i.e., AvailTCs), but rather type/class and method/label names,
causing the renamer to (semi)randomly report instance methods as
being out-of-scope in the presence of multiple imports for a module.
* didn't support 'hiding' of class / method names (for the purposes
of checking instance decls).