Added Help key handling (as Insert) on Mac OS X.

area.go

@@ -187,7 +187,7 @@ type KeyEvent struct {
 type ExtKey uintptr
 const (
 	Escape ExtKey = iota + 1
-	Insert
+	Insert		// equivalent to "Help" on Apple keyboards
 	Delete
 	Home
 	End

events_darwin.go

@@ -90,7 +90,7 @@ var keycodeExtKeys = map[uintptr]ExtKey{
 	0x67:	F11,
 	0x6D:	F10,
 	0x6F:	F12,
-//	0x72:	kVK_Help,
+	0x72:	Insert,		// listed as the Help key but it's in the same position on an Apple keyboard as the Insert key on a Windows keyboard; thanks to SeanieB from irc.badnik.net and Psy in irc.freenode.net/#macdev for confirming they have the same code
 	0x73:	Home,
 	0x74:	PageUp,
 	0x75:	Delete,

todo.md

@@ -3,8 +3,7 @@ MAC OS X:
 	- asked: http://stackoverflow.com/questions/23046414/cocoa-how-do-i-get-nscombobox-indexofselecteditem-to-return-1-if-the-user-m
 - 10.6 also spits a bunch of NSNoAutoreleasePool() debug log messages even though I thoguht I had everything in an NSAutoreleasePool...
 - OS X: key up with a modifier held and our new modifiers code doesn't seem to happen?
-- OS X: handle Insert/Help key change in a sane and deterministic way
-	- will need old and new Mac keyboards...
+- figure out how to bypass the window manager's Help key handling
 - point out that Areas get keyboard focus automatically on click on Mac OS X
 - make sure Areas get keyboard focus when clicking outside the actual Area space on Mac OS X