testkit: Fix NTSC 8361 "Thin Agnus" detection.
testkit: Fix NTSC 8361 "Thin Agnus" detection.

Reports ID 00 even though an NTSC Agnus should report 10.

In the case of ID 00 we fall back to measuring CIA tick frequency
against the VBlank frequency to detect PAL/NTSC crystal.

Fixes #23

keirf/Amiga-Stuff,keirf/Amiga-Stuff