implement some basic SID3 effects

Wave/PCM chan and pw/cutoff slides coming later ig

src/engine/dispatch.h

@@ -265,6 +265,14 @@ enum DivDispatchCmds {
 
   DIV_CMD_FDS_MOD_AUTO,
 
+  DIV_CMD_SID3_SPECIAL_WAVE,
+  DIV_CMD_SID3_RING_MOD_SRC,
+  DIV_CMD_SID3_HARD_SYNC_SRC,
+  DIV_CMD_SID3_PHASE_MOD_SRC,
+  DIV_CMD_SID3_WAVE_MIX,
+  DIV_CMD_SID3_LFSR_FEEDBACK_BITS,
+  DIV_CMD_SID3_1_BIT_NOISE,
+
   DIV_CMD_MAX
 };