clrs; exercise 10.3.1 - illustrate "hand-rolled" memory
clrs; exercise 10.3.2 - ALLOCATE-OBJECT and FREE-OBJECT
clrs; exercise 10.3.3 - why don't we reset prev?
clrs; exercise 10.3.4 - keeping the list compact
clrs; exercise 10.3.5 - COMPACTIFY-LIST