Fix generate tag from address (servers.c)

[baytuch]

This commit fixed the generation of the tag from the address in such a way as to contain a name. For example: IRC.it-hobby.km.ua-> it-hobby.

[ailin-nemui]

it does change the behaviour at least in one case to the worse

old example:
irc-2.cs.hut.fi -> hut

with your code:
irc-2.cs.hut.fi -> cs

[baytuch]

My project is hosted in a second level domain so I would like the tag to be the project name and not the second level domain.