sig_analog: Allow '#' to end the inter-digit timeout when dialing.

sig_analog: Allow '#' to end the inter-digit timeout when dialing.

It is customary to allow # to terminate digit collection immediately
when there would normally be a timeout. However, currently, users are
forced to wait for the timeout to expire when dialing numbers that
are prefixes of other valid matches, and there is no way to end the
timeout early. Customarily, # terminates the timeout, but at the moment,
this is just rejected unless there happens to be a matching extension
ending in #.

Allow # to terminate the timeout in cases where there is no dialplan
match. This ensures that the dialplan is always respected, but if a
valid extension has been dialed that happens to prefix other valid
matches, # can be used to dial it immediately.

Resolves: #1510