Similar to the xterm AllowWindowOps option, this is an option to allow or
disallow certain (non-interactive) operations that can be insecure or
exploited.

NOTE: xsettitle() is not guarded by this because st does not support printing
the window title. Else this could be exploitable (arbitrary code execution).
Similar problems have been found in the past in other terminal emulators.

The sequence for base64-encoded clipboard copy is now guarded because it allows
a sequence written to the terminal to manipulate the clipboard of the running
user non-interactively, for example:

printf '\x1b]52;0;ZWNobyBoaQ0=\a'

Scroll is a program that stores all the lines of its child and be used in st as
a way of implementing scrollback.

This solution is much better than implementing the scrollback in st itself
because having a different program allows to use it in any other program
without doing modifications to those programs.

Previously mouse shortcuts supported only ttywrite.

This required adding an "Arg" function ttysend - which does what the
original mouse shortcuts did.

"use iswspace()/iswpunct() to find word delimiters

    this inverts the configuration logic: you no longer provide a list of
    delimiters -- all space and punctuation characters are considered
    delimiters, unless listed in extrawordchars."

Feedback from IRC and personal preference.

this inverts the configuration logic: you no longer provide a list of
delimiters -- all space and punctuation characters are considered
delimiters, unless listed in extrawordchars.

And move it to the patches section.
Keeping it would force to add an exec pledge on OpenBSD, and some
people think it's bloated, so bye!

Signed-off-by: Devin J. Pohly <djpohly@gmail.com>