fixed a potential stack corruption

hdlcio.c

@@ -42,7 +42,7 @@ unsigned int i,j;
 char ch;
 
 for (i=0;i<len;i+=16) {
-  printf("%08x: ",(unsigned long)(base+i));
+  printf("%08lx: ",(unsigned long)(base+i));
   for (j=0;j<16;j++){
    if ((i+j) < len) printf("%02x ",buffer[i+j]&0xff);
    else printf("   ");