Flags in property lists

[David A. Moon <Moon at MIT-MC>]

Flat property lists can be stored more efficiently than pair lists
in Lisp with cdr-coding.  That isn't why Maclisp dropped them, of
course; probably Maclisp dropped them because they are a crock and
because they make GET a little slower, which slows down the
interpreter in a system like Maclisp that stores function definitions
on the property list.