SuperAccessors

This class adds super accessors for all super calls that either appear in a trait or have as a target a member of some outer class.

It also checks that:

(1) Symbols accessed from super are not abstract, or are overridden by an abstract override.

(2) If a symbol accessed from super is defined in a real class (not a trait), there are no abstract members which override this member in Java's rules (see SI-4989; such an access would lead to illegal bytecode)

(3) Super calls do not go to some synthetic members of Any (see isDisallowed)

(4) Super calls do not go to synthetic field accessors