It is not possible to specify a TTL for the discover function

[gabrielmagno]

When broadcasting to discover new devices, it is useful to be able to specify a TTL, which is an UPnP feature that allows finding devices that are in more than one hop of distance from the host (e.g. a multi-router home network). This is related to this similar issue in the ssdp-client library.

Considering that the ssdp_client::search function now have the TTL option, the fix is as simple as exposing the TTL parameter to therupnp::discover function.