add class/instance measure types.

parse and thread through to Constraint
add expected constraints and types
give measures multiple defs instead of dealing with substitutions
ugh, something stupid with the new CPP on osx i think..
Merge branch 'master' of github.com:ucsd-progsys/liquidhaskell into type-class

Conflicts:
	Language/Haskell/Liquid/Bare.hs
ugh, still need to check instance methods match class
fallback to lookupGhcVar in varSymbols

this is necessary for type-class methods, which have no definition in
the corebinds
cleaning up and preventing a crash due to type families
Merge pull request #137 from gridaphobe/type-class

Add preliminary support for attaching specs to type class methods