Remove all of the old stack system

Remove all of the old stack system

* Source/DebuggerController.h: Remove stackController2 and stack ivars
* Source/DebuggerController.m:
(validateUserInterfaceItem:): Update to use stackController.stack for -[count]
(resetDisplays): Remove the call to stackController2
(setStack): Removed
(stepIn:): Call -[updateStackViewer]
(stepOut:): ditto
(stepOver:): ditto
(updateSourceViewer): Use our new stackController
(updateStackViewer): New method
* Source/GDBpConnection.m:
(updateStackTraceAndRegisters): Remove the block of code that used to update the stack