I will add daemonizing when two conditions are met...
1) Someone confirms that it works.
2) Someone confirms that it works on Linux.

I'm particularily worried about the comWriteByte() and comWriteString()
error handling (or lack thereof)... Especially in modem_send()

Also, I think the timeout mechanism should be in comReadByte() itself
so we don't need to use while(1) { poll(); yield(); } loops.

I assume that Win32 supports read timeouts... if not, a single loop and
only for Win32 would be preferable to having it multiple places.