成员的完整列表，这些成员属于 _vrpn_TRACKERWORKSPACECB,包括所有继承而来的类成员

msg_time (定义于 _vrpn_TRACKERWORKSPACECB)	_vrpn_TRACKERWORKSPACECB
workspace_max (定义于 _vrpn_TRACKERWORKSPACECB)	_vrpn_TRACKERWORKSPACECB
workspace_min (定义于 _vrpn_TRACKERWORKSPACECB)	_vrpn_TRACKERWORKSPACECB