libraries-and-tools.md: add C++ client package

Documentation/libraries-and-tools.md

@@ -61,6 +61,8 @@
 **C++ libraries**
 - [edwardcapriolo/etcdcpp](https://github.com/edwardcapriolo/etcdcpp) - Supports v2
 - [suryanathan/etcdcpp](https://github.com/suryanathan/etcdcpp) - Supports v2 (with waits)
+- [nokia/etcd-cpp-api](https://github.com/nokia/etcd-cpp-api) - Supports v2
+- [nokia/etcd-cpp-apiv3](https://github.com/nokia/etcd-cpp-apiv3) - Supports v3
 
 **Clojure libraries**