This commit adds the connect() method to the PPP interface and requires
that connect() be called after active(1). This is a breaking change for
the PPP API.
With the connect() method it's now possible to pass in authentication
information for PAP/CHAP, eg:
ppp.active(1)
ppp.connect(authmode=ppp.AUTH_PAP, username="user", "password="password")
If no authentication is needed simply call connect() without any
parameters. This will get the original behaviour of calling active(1).
b6906fa573