BDeskbar & Deskbar: export window bool settings to BDeskbar

Add methods to get and set "Always on top", "Auto raise", and "auto hide"
which are all booleans which control aspects of the Deskbar window to
BDeskbar.

Set the bool to the default value initially. Check if sending the
message succeeds, if so check the reply which also fills out the bool.
Don't check to see if reply succeeded because the bool will only be
overwritten if it did.

Follow the BDeskbar convention Is...() for getter, Set...() for setter
e.g IsAlwaysOnTop() is the getter, SetAlwaysOnTop() is the setter.

Define new message constants to call the newly created methods.
Follow BDeskbar convention: 'gtla' is used for getter, 'stla' for setter.
g/s for getter/setter, tla is an all-lowercase code unique to each
getter/setter pair.

Copy/paste these message constants into BarApp.h unchanged. Replace four
letter codes with imported message constants in BarApp.cpp and
BarWindow.cpp. Much nicer than using bare codes.

The new BDeskbar methods are all handled by TBarApp. The getters send
back a reply message containing the bool while the setters fall through
to existing setter cases.

headers/os/interface/Deskbar.h

@@ -41,6 +41,15 @@ public:
 			bool				IsExpanded() const;
 			status_t			Expand(bool expand);
 
+			bool				IsAlwaysOnTop() const;
+			status_t			SetAlwaysOnTop(bool alwaysOnTop);
+
+			bool				IsAutoRaise() const;
+			status_t			SetAutoRaise(bool autoRaise);
+
+			bool				IsAutoHide() const;
+			status_t			SetAutoHide(bool autoHide);
+
 	// Item querying methods
 			status_t			GetItemInfo(int32 id, const char** _name) const;
 			status_t			GetItemInfo(const char* name, int32* _id) const;