bug#15246: Info: Document M-x visible-mode RET

[Jambunathan K]

Info: Document M-x visible-mode RET

A handy command particularly while working with modes like Org which
routinely "hides" the buffer text.  For example, hyperlinks.

    [[http://www.google.com][Google]]



Just looking at simple.el, I realize that there is multiple ways to
toggle.

    M-x visible-mode 

    M-x toggle-word-wrap

    M-x turn-on-auto-fill

Turning on, why there be multiple causes for it?  May be some
normalization could be adopted.