Fix the superclass translation for instance decls
			Merge to STABLE

There is a long-standing difficulty whereby it's surprisingly easy 
to accidentally generate an entirely-bogus recursive dictionary when 
generating the definitions for the superclasses of an instance decl.

The problem arises because the default story is that whenever we
add a constraint to our pile of solved constraints, we automatically
add all its superclasses.  But that is simply wrong when we are trying
to generate superclasses. 

Solution: do no auto-superclass addition when solving the superclass
constraints of an instance declaration.  I think should fix it once and
for all.  

	tcrun021, tcrun033 are test cases

tcrun033 showed up the bug; thanks to Simon Foster and Ralf Laemmel.