(setq byte-compile-warnings '(unresolved)) does not work

[Matt Swift]

Setting `byte-compile-warnings' to '(unresolved) results in no
compiler warnings about unresolved functions in 21.2 and this week's
CVS Emacs 21.3.  The reason is that the list
`byte-compile-unresolved-functions' is maintained properly only when
the 'callargs and 'redefine warnings are also selected.

The list is augmented only in `byte-compile-callargs-warn', which is
called only if the 'callargs warning is selected.

The list is trimmed only in `byte-compile-defalias-warn' and
`byte-compile-if', which are called only when compiling invocations of
`defalias' and `if', and `byte-compile-arglist-warn', which is called
only if the 'redefine warning is selected.

To demonstrate, save the following in its own file and \C-x\C-e
(`eval-last-sexp') with point at the end.  Uncomment `callargs' and
repeat.

;;;;;;;;;;;;;;;;;;;;;;

(or
 (and (fboundp 'zzzz) (progn (zzzz) (error "whoops")))
 (and
  (setq byte-compile-warnings '(
                                unresolved
                                ;; callargs
                                ))
  (byte-compile-file (buffer-file-name))))