games/dMagnetic: Update to 0.24

• Simplify test suite. [1]

• Switch manpages to the preferred share/man location while I'm here.

Changelog:

• It is now possible to use .d64 images to play the games.

• The test suite can now be called directly via its own "do-test" target per sub-make. [1]

PR: 247915
Submitted by: Thomas Dettbarn <dettus@dettus.net> (maintainer)