Anonymous methods indices should not be global

[nicolasstucki]

class Foo {
  def foo() = {
    def f() = ()
    f()
  }
}
class Bar {
  def foo() = {
    def f() = ()
    f()
  }
}

will have the f lifted as f$1 and f$2, but they should be both f$1 as they are in different classes. Currently, the result of the code depends on the compilation order.

This is a follow-up of #2964.