Add remaining solutions to exercises in subsection 2.3.3

This was quite a long one, since I decided to both implement support for
constructing exponent ops, and also made sure that the expressions get
reasonably optimized once they are constructed.

chapter-2/ex-2.53.txt

@@ -0,0 +1,7 @@
+(list 'a 'b 'c) -> (a b c)
+(list (list 'george)) -> ((george))
+(cdr '((x1 x2) (y1 y2))) -> ((y1 y2))
+(cadr '((x1 x2) (y1 y2))) -> (y1 y2)
+(pair? (car '(a short list))) -> #f
+(memq 'red '((red shoes) (blue socks))) -> #f
+(memq 'red '(red shoes blue socks)) -> (red shoes blue socks)