synthetic super call positioning is suboptimal

[scabug]

Side issue noticed in #8367, the error message related to a synthetic super call is positioned confusingly at a comment.

class C



// comment

Positioned as:

[[syntax trees at end of                    parser]] // newSource1.scala
[6]package [6]<empty> {
  [6]class C extends [7][21]scala.AnyRef {
    [21]def <init>() = [21]{
      [NoPosition][NoPosition][NoPosition]super.<init>();
      [21]()
    }
  }
}

This led me to try this patch: scala/scala#3612

But there is a bit more work needed to finesse this (as always with positions), so I'm lodging this as a ticket for now.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8389?orig=1
Reporter: @retronym
Affected Versions: 2.11.0