multimedia/libzen: Update to 0.4.40

* Use proper upstream version
* Switch to separate source archives
* Switch to CMake which brings us much closer to other distributions
* Sanitize source code

Reference: https://github.com/MediaArea/ZenLib

Changelog: https://github.com/MediaArea/ZenLib/releases/tag/v0.4.40

PR:		268707
Approved by:	portmgr (maintainer timeout, 2+ weeks)