www/privoxy: Update 4.1.0 => 4.2.0

Privoxy 4.2.0 fixes a couple of bugs and brings general improvements
such as support for elliptic-curve keys.
Two potential security problems have been reported and addressed.

Changelog:
https://lists.privoxy.org/pipermail/privoxy-announce/2026-June/000013.html

Port changes:

• The Privoxy tools come with proper man pages now so install them when the tools are enabled.

PR: 295848
Reported by: Fabian Keil <fk@fabiankeil.de> (maintainer)
Approved by: osa, vvd (Mentors, implicit)
MFH: 2026Q2

(cherry picked from commit c9cc3d36733d5f4f0ce5ae4f6b3ce02ca868384c)