Fixed: remove non-standard CPDocument API "firstEligibleExistingWindowController".

This method did not actually do anything, and was not part of the expected CPDocument API.

Refs #1870.

AppKit/CPDocument.j

@@ -244,11 +244,6 @@ var CPDocumentUntitledCount = 0;
 {
 }
 
-- (CPWindowController)firstEligibleExistingWindowController
-{
-    return nil;
-}
-
 // Creating and managing window controllers
 /*!
     Creates the window controller for this document.