Comment 5 for bug 1190240

memcached_server_instance_st seems to have disappeared in 1.0.17

As a result, code like this:

```
static memcached_return
_PylibMC_AddServerCallback(memcached_st *mc,
                           memcached_server_instance_st instance,
                           void *user) {
...
    desc = PyString_FromFormat("%s:%d (%u)",
            memcached_server_name(instance), memcached_server_port(instance),
            (unsigned int)context->index);
...
}
```

fails to compile with:

```
src/_pylibmcmodule.c:1848: error: expected declaration specifiers or '...' before 'memcached_server_instance_st'
src/_pylibmcmodule.c: In function '_PylibMC_AddServerCallback':
src/_pylibmcmodule.c:1896: error: 'instance' undeclared (first use in this function)
```

Question: Was removing memcached_server_instance_st intentional? Should we be using some other API now?