Implement a flag to display logger or not

In a multi-part project (consider termcaps, parser, job control, hum). To remove the output of the logger for some part, implement a flag.

```
general : L_G 0x01
termcaps : L_T 0x02
parser : L_P 0x04
job : L_J 0x08
```

and call the logger like it : 

```
log_info(L_P | L_T, "%s", "log message");
```

This will display messages for general (everytime), parser and terncaps, but not job control.
