DAHDI has nice readable names for each span, there's no need to do any channel
calculations by hand. This change searches for a span with the specified name
and will use it's offset as the channel offset.
[octoi]
type=E1
offset=279
[auerswald]
type=E1
offset=31
becomes:
[octoi]
type=E1
span=trunkdev/octoi/0
[auerswald]
type=E1
span=TE8/0/2
which should be more reliable and less error-prone in the long run.