cad/z88: update 13.0 -> 15
- Changes PORTVERSION to DISTVERSION
- Sets submitter as MAINTAINER.
- Uses USE_GITHUB instead of MASTER_SITES
- Sets LICENSE
- Sets appropriate dependencies, USES, USE_X
- Adds an EXAMPLES option
- Adds a pkg-message to explain how the port must be used, as it is not self-evident (The software assumes all files in the same directory instead of distributed into bin/, ${DATADIR} etc so I had to find a work around: the solution is easy for the user).
PR: 233772
Submitted by: Lorenzo Salvadore <phascolarctos@protonmail.ch>
Reviewed by: chitty_cloud@me.com
Relnotes: https://forum.z88.de/viewtopic.php?f=18&t=885