Allow whitespace before comma in two-general-operand instructions.

(it was allowed already in other cases such as SOB, JSR, ASH, ...).

assemble.c

@@ -1201,6 +1201,7 @@ static int assemble(
                                 return 0;
                             }
 
+                            cp = skipwhite(cp);
                             if (*cp++ != ',') {
                                 report(stack->top, "Illegal syntax\n");
                                 free_addr_mode(&left);