Strongly type the cell of NSTextField
NSTreeController.Content property should be NSObject, not NSTreeController

See https://bugzilla.xamarin.com/show_bug.cgi?id=13792
Fix NSDocumentChangeType

As per https://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSDocument_Class/Reference/Reference.html#//apple_ref/doc/c_ref/NSDocumentChangeType
Merge pull request #120 from rzhw/patch-1

Fix NSDocumentChangeType
Merge pull request #117 from dlech/patch-1

NSTreeController.Content property should be NSObject, not NSTreeController
Apply the core fix for #13771
Merge pull request #113 from justinvp/master

Strongly type the cell of NSTextField
New CoreWlan bindings with support for new APIs
Merge with old APIs