Add prefix_none.h for GRP4 instruction handling

Author: greydoubt

src/cpu/core_normal/prefix_none.h

@@ -0,0 +1,22 @@
+CASE_B(0xfe)               /* GRP4 Eb */
+    {
+	    GetRM;Bitu which=(rm>>3)&7;
+	    switch (which) {
+			case 0x00:     /* INC Eb */
+			    RMEb(INCB);
+			    break;
+			case 0x01:     /* DEC Eb */
+			    RMEb(DECB);
+			    break;
+			case 0x07:     /* CallBack */
+			    {
+			        Bitu cb=Fetchw();
+			        FillFlags();SAVEIP;
+			        return cb;
+			    }
+			default:
+				E_Exit("Illegal GRP4 Call %d",(rm>>3) & 7);
+				break;
+	    }
+	    break;
+    }