made acceptable for flex (no yyless() callable from other source file)

modules/src/em_opt/parser.g

@@ -487,7 +487,7 @@ LLmessage(insertedtok)
 	fprintf(stderr,"parser: syntax error on line %d: ",linenum);
 	if(insertedtok) {
 		fprintf(stderr,"Inserted token %d\n",insertedtok);
-		yyless(0);
+		back_token();
 	}
 	else fprintf(stderr,"Deleted token %d\n",LLsymb);
 }

modules/src/em_opt/syntax.l

@@ -58,3 +58,8 @@ offset		return(OFFSET);
 \n		{ linenum++; return(yytext[0]);}
 .		return(yytext[0]);
 %%
+
+back_token()
+{
+	yyless(0);
+}