Fix server_version parsing

[mkabilov]

Server version string can consist of 2 parts, not always 3

[cheald]

This has implications for CopyIn usage - when the detected server version is less than 9.0, it falls back to a much slower Sprintf encoding. Merge would be appreciated!

My local startup parses:

server_version
10.5 (Ubuntu 10.5-0ubuntu0.18.04) => input does not match format

So the server version ends up being 0, which then falls back to the slower version.

[Lekensteyn]

This solves the same issue as #979 but is more complex. I would suggest merging #979 and closing this one. What do you think?