Use fptest as testing framework

[Free-Pascal-meets-SDL-Website]

This PR

• adds support for the fptest testing framework
• modifies fptest to allow checking for pointers (a PR for this is pending)
• applies a MacOS fix for the EpikTimer unit (the fix is already committed by someone else but still pending)
• adds SDL2.dll to allow running the test suite also under the Windows remote machine
• as of now performs the "init test" and the "version test" (as seen before)

ATTENTION Before merging, the triggering branch "use-fptest" has to be removed from ci.yml!