Option: XU USER SIGN-ON

This is a protocol option to link other packages that want to know about
a user sign-on  event.
The protocols must not read/write to the screen because we may be doing a
GUI sign-on.  They can set Text that will be displayed to the user by
calling SET^XUS1A(string)  The first character should be a "!" to cause the
text to be placed on a new line. DUZ will be defined but other variables
may not be.
It is called from XUS1A.