Mention `frame-resize-pixelwise' to make frames truly fullscreen or maximized.

Mention `frame-resize-pixelwise' to make frames truly fullscreen or maximized.

* frame.el (toggle-frame-maximized, toggle-frame-fullscreen):
In doc-string mention need of setting `frame-resize-pixelwise'.

* frames.texi (Frame Commands):
* cmdargs.texi (Window Size X): Mention the use of
`frame-resize-pixelwise' to make frames truly fullscreen or
maximized.

* frames.texi (Size Parameters, Size and Position): Mention that
with some window managers you have to set
`frame-resize-pixelwise' in order make a frame truly fullscreen
or maximized.