Sets up goto-address functionality in the current buffer.
Allows user to use mouse/keyboard command to click to go to a URL
or to send e-mail.
By default, goto-address binds `goto-address-at-point' to mouse-2 and C-c RET
only on URLs and e-mail addresses.
Also fontifies the buffer appropriately (see `goto-address-fontify-p' and
`goto-address-highlight-p' for more information). (fn)