Toggle global newline visualization (Global Whitespace Newline mode).
With a prefix argument ARG, enable Global Whitespace Newline mode
if ARG is positive, and disable it otherwise. If called from
Lisp, enable it if ARG is omitted or nil.
Use `global-whitespace-newline-mode' only for NEWLINE
visualization exclusively. For other visualizations, including
NEWLINE visualization together with (HARD) SPACEs and/or TABs,
please use `global-whitespace-mode'.
See also `whitespace-newline' and `whitespace-display-mappings'.
(fn &optional ARG)
Non-nil if Global-Whitespace-Newline mode is enabled.
See the command `global-whitespace-newline-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `global-whitespace-newline-mode'.