We now remember which items in the register have been expanded so they stay open

We now remember which items in the register have been expanded so they stay open

* Source/DebuggerWindowController.h: Adding an _registerView outlet and an _expandedRegisters array
* Source/DebuggerWindowController.m:
([DebuggerWindowController initWithConnection:]): Initialize _expandedRegisters
([DebuggerWindowController dealloc]): Release _expandedRegisters
([DebuggerWindowController setRegister:]): When we set the register, go through all the items and see if any of them should be expanded
([DebuggerWindowController outlineViewItemDidExpand:]): Add the expanded object to _expandedRegisters
([DebuggerWindowController outlineViewItemDidCollapse:]): Remove the object from _expandedRegisters
* English.lproj/Debugger.nib: Hooking up the _registerView outlet