GET-PUSH-BUTTON-LABEL
=====================

syntax: (get-push-button-label <babylon-push-button>)

This function returns the text from the push-button-
label.

example: >(define-task LABEL-DEMO-TASK (interface)
             :documentation "This is a demo"
             actions
             (setf new-text-label (kb-prompt "How do
             you want to call the push-button ~s ?~%" 
             "please push"))
             (if (stringp new-text-label)
             (set-push-button-label
             (get-window-element
             interface "pb1") new-text-label)
             (kb-format "The input ~s was false!
             please enter a string next time!" new-
             text-label))
             (kb-format "~10T- the push-button
             is called ~s~%"
             (get-push-button-label
             (get-window-element interface "pb1"))))