The two-argument form of defvar

[Philipp Stephani]

Hi,

when looking at the source code of defvar it becomes clear that the
two-argument form

(defvar foo)

is a no-op. It is often used as a signal to the byte compiler that a
certain variable will be available, similar to declare-function. Would it
be possible to clarify the docstring accordingly? Currently it has no
indication that the two-argument form doesn't do anything.