Added APROP_StencilColor for Set/GetActorProperty
Added GetActorPowerupTics special
Update zdefs.acs with shadow and subtract styles. 

I'm not sure why the values jump from 1, 2, 3, 4, 5 to 64, 65, 66, 67, but I continued from there. Adding shadow is necessary to add subtract.
- ChangeActorAngle/Pitch added to zspecial.acs.
- new render styles.
Merge branch 'master' of https://github.com/rheit/acc