Code review comment for lp://staging/~gary-wzl77/net-cpp/dual_landing_support

Okay, here's a list of todo items before we can land this:

1. split the speed limit/duration member of Request::Configuration out and allow the user to configure it through an extra method on the Client class.

2. Ensure that the defaults for this setting match what previous net-cpp did. The current limit=1, duration=30s values seem different to the default:

https://curl.haxx.se/libcurl/c/CURLOPT_LOW_SPEED_LIMIT.html (limit=0)
https://curl.haxx.se/libcurl/c/CURLOPT_LOW_SPEED_TIME.html (duration=0)

3. Set SOVERSION to 1 for vivid, and 2 for anything else.

3. Resurrect the libnet-cpp1.symbols file from current trunk, and the libnet-cpp2.symbols file from the current net-cpp package in yakkety. Both files would need to be updated to include the new methods on Client.

Alternatively, ship libnet-cpp1.shlibs and libnet-cpp2.shlibs files with appropriate contents, but it is probably going to be easier to prove things are compatible to the landing team by sticking with the existing symbols files.