READ-DELIMTED-LIST and dots

[Guy Steele <gls@THINK-AQUINAS.ARPA>]

I propose that READ-DELIMITED-LIST be extended by adding one
more optional argument, dot-permitted-p, defaulting to nil,
that if true allows the delimited list to contain dot notation,
and if false forbids dot notation.

Right now the manual does not address the question of dot notation
in this context, and at least one implementation does not
permit dot notation in delimited lists, which makes that function
useless for simulating the action of "(".