Fix type inferencing, syntax highlighting and code navigation for extension methods that override Object methods

[eric-milles]

Consider the following:

String test(String[] array) {
   array.toString()
}

When executed, DefaultGroovyMethods.toString(Object[]) is used. However, it is displayed in the editor as Object.toString(). When static compilation is enabled, the extension method connection is clear.

vs.

[eric-milles]