implementing typing rules for use-site variance
ws
almost-complete impl of member typing for use-site variance
member typing and inheritance with use-site variance
fix to grammar
fix applyVarianceOverrides
fix subtyping rules for use-site variance
fix problem where getSupertype() returned Nothing
Co<in T> is a subtype of Co<Anything>, Contra<out T> of Contra<Nothing>
disallow attempt to override variance of param with declared variance
disallow variance annotations in extended/satisfied type
Inv<out Anything> == Inv<in Nothing>
fix lexing of >=> for #1018
fix parsing of [X<T>=] and (X<T>=) for #1018
minor fix
fix member typing for use-site variance annotations in qualifying types
Clarify that bounded comparison evaluates x only once

The old definition

    l<x<u means x>l && x<u

could have been misunderstood to mean that x would be evaluated twice.
Rectify this using 'let'.
Remove 'satisfies' from operator table

Not yet supported!
apparently, I place too much trust in Eclipse's Inline refactoring
also, fix condition on caching
implement Inv<out Nothing>==Inv<Nothing>,Inv<in Anything>==Inv<Anything>
and fix some logic problems in equivalence algorithm