Type questions

[Christopher Fry <cfry@OZ.AI.MIT.EDU>]

- What's the relationship between keyword, the type,
  and keyword, a symbol in the keyword package?
  Spicelisp calls the type keyword a subtype of symbol.

- is (subtype foo foo) true for any valid type foo ?

- Are the new types: signed-byte and unsigned-byte
  subtypes of fixnum, like bit is?

- In Spicelisp, COMMON is a subtype of ATOM and
  ATOM is a subtype of COMMON. True in CL? 

CLtL should have explicite paragraphs and index entries
for every type. I noticed BIT and KEYWORD lacked this
kind of documentation.