Fixed Special Color Calculation mode 2

When Special Color Calculation mode, aka "per dot color calculation",
the transparency is based on "color code" not color.

Thanks vbt for reporting the bug and providing a demo to test it.

git-svn-id: svn+ssh://svn.code.sf.net/p/yabause/code/trunk@3252 d7be59e3-070e-4b9a-85a1-4646befae34d