[Cs3] figure registry code modification

[Mikhail Nesterenko]

CS3 students,

There was a discussion about shortening code and eliminating a
switch() in random figure selection in the below example presented in
class.

http://antares.cs.kent.edu/~mikhail/classes/cs3/Examples/Prototype/prototypeFiguresRegistry.cpp

I went ahead and did the modification. Try to figure out what is
happening in code after the following comment:

	 // allocate a few random squares, lines and triangles

Thanks,
-- 
Mikhail