the multit regression test checks the following multitexture features:

2. tick based framestep
   -- this need to be aborted earlier than the loop due to certain
      timing conditions leading to the problem of the engine managing
      one or a few framesteps more before the engine finally terminates.

2. manually selecting frameset active image
3. multitexturing sampled by shader

and covers the bug described by #87 on github.

the multitexturing uses not covered are multitexturing 3d models
and round-robin storage.
