Ddclient 3.8.3 released

Yet again it's been a while but here is new release of ddclient. As usual,
there are some important changes and some documentation is modified.
A detailed overview can be found in ChangeLog but here's a quick overview:

• added Alpine Linux init scritp - patch send by @Tal on github.
• adding support for nsupdate - patch send by @droe on github
• allow log username-password combinations - patch send by @dirdi on github
• adding support for cloudflare - patch send by @roberthawdon on github
• adding support for duckdns - patch send by @gkranis

A very big thank you for everyone who created a pull request on github and
for everyone who helped to fix the little issues caused by the new providers.