Implementation note: the so instrumented sprites use actor[].t_data[7] to hold a magic number (0x18190000 + pivot spr idx), and t_data[8] and [9] for the initial coords relative to the pivot point.
git-svn-id: https://svn.eduke32.com/eduke32@1913 1a8010ca-5511-0410-912e-c29ae57300e0