Put the log and scratch text in the same window.

Put the log and scratch text in the same window.

This is a step towards Ticket #40360 without going all the way.  You can
open additional viewer windows.  They are not connected by an
Oberon-style messaging system (yet.  It would be nice to use the Tk event
system for that.)

This way the log and the main/scratch/system-menu text are conceptually
unified in the (equivelent of "desktop") base metaphor of the system.