fix bugs on code generation in juliac-core, add method...

fix bugs on code generation in juliac-core, add method UnifiedClass.getInstanceMethods() (name of the method should be reconsidered) who permits to get all public methods usable by the calling UnifiedClass (should be implemented for UCtClass), and add UnifiedMethod.getDeclaringClass() who permits to get the UnifiedClass who is responsible for UnifiedMethod.