Currently FirThisReceiverExpression of instance methods are translated
to references of the class' thisReceiver,
not the method's dispatch receiver,
which causes problems with IrFrameMap::typeOf,
as the class' thisReceiver is not in the typeMap.
This commit translates non-qualified "this" references of
instance methods to references of the methods' dispatch receiver.
Current implementation of calls with super qualifier relies on
invokespecial, which has some more constraints than regular virtual
invocations. When those constraints aren't met, accessors are needed.