This commits checks iterator/hasNext/next functions whether they are
declared as operator or not. Also, it changes logic of hasNext/next
error reporting, now we're able to report errors about both these
functions.
- locals win
- unary calls to plus/minus are not supported in favor of unaryPlus/unaryMinus
- unqualified nested classes are temporarily reported as unresolved
- function without receiver win against extension function
- explicit import win against star import
Mikhail Glukhikh