Change the style of --[no]opt negatable options

This applies to all tools. We have L<"--[no]-foo"> all over the place; I'd like to change the docs so they just list --foo as negatable and we don't have to list them with the optional negatableness. So it'd be like this:

=item --foo

negatable: yes

Redesigned Bash tools have this style, but it's going to be very slow going changing all the tools.