* nx.tcl, xotcl2.tcl: Fully qualify uses of Tcl's upvar and uplevel, to avoid confusion when introducing equally named procs/ cmds in the OS namespaces.
- added new variant of "volatile" trying to mimick the XOTcl1 volatile behavior. - added experimental feature NSF_WITH_TCL_OBJ_TYPES_AS_CONVERTER, which uses registered TclObjTypes as value checkers (currently deactivated)