Fix dependency analysis (notably bindInstsOfLocalFuns) in TcBinds

Fix dependency analysis (notably bindInstsOfLocalFuns) in TcBinds

GHC 6.5 does enhanced dependency analysis for recursive bindings, to
maximise polymorphism based on type signatures.  (See Mark Jones's
THIH paper.)

I didn't do the bindInstsOfLocalFuns part correctly though, and jhc
showed up the bug.  (It only matters when you have a recursive group
of two or more functions with a type signature, not at top level, which
is why it hasn't shown up till now.)

Test is tc207.hs