Fix to "cannot connect to ISP Orange in France"

[Jacques Goldberg <Jacques.Goldberg@xxxxxxx>]

For archiving purposes:

Symptom:
- observed with Ubuntu 7.10
- pppd session sets up local IP, remote (P-t-P) IP, DNS addresses.
- P-t-P address does not respond to ping.

Fix:
- add replacedefaultroute in /etc/ppp/options.

Notes:
- Could also happen with other ISP's.
- Clearly ISP dependent.
- may be connected with the "roaming" feature of Ubuntu 7.10 network 
manager.