In GNU Emacs 23.0.60.23 (i686-pc-linux-gnu, GTK+ Version 2.12.9) of
2008-12-12 on escher 

According to the argument-list of declare-function, only its first two
arguments are obligatory.  But by rgrepping emacs/lisp for
"(declare-function" I found four invocations with `nil' as the third
argument (there are many more invocations with only two arguments):

./calendar/todo-mode.el:914:(declare-function calendar-current-date "calendar" nil)
./progmodes/fortran.el:917:(declare-function gud-find-c-expr "gud.el" nil)
./smerge-mode.el:1079:(declare-function ediff-cleanup-mess "ediff-util" nil)
./subr.el:2251:(declare-function w32-shell-dos-semantics "w32-fns" nil)

Patches attached.