Spec update: overloading resolution tweaks
Spec update: overloading resolution tweaks

Propagate more type information to improve eta-expansion
and function parameter type inference for polymorphic,
higher-order overloaded methods.

martijnhoekstra/scala,scala/scala,martijnhoekstra/scala,lrytz/scala,martijnhoekstra/scala,martijnhoekstra/scala,martijnhoekstra/scala,scala/scala,lrytz/scala,lrytz/scala,lrytz/scala,scala/scala,lrytz/scala,martijnhoekstra/scala,scala/scala,scala/scala,scala/scala,lrytz/scala