WIP: add a stub IRC daemon named `kike'

As it is going to share a great lot of functionality with ZyklonB, I have
decided to extract the common parts into `common.c' and make the two subprojects
include this file.

The Single Compile Unit concept has proven valuable (sub-second compile times,
dead code warnings, almost no need for function declarations, whole-program
optimizations), and the sources aren't that long so far anyway.

I am probably going to add CMake support later but so far it's not a priority.
This project is meant to be portable and freely relocatable (ie. no hardcoded
paths if I can avoid it).
Add .gitignore
Implement parsing of IRC 3.2 message tags

It's still in the making and we don't use it, but let's not fail on it if e.g.
a plugin decides to enable it.
Implement an iterator for `struct str_map'
Move `SSL_CTX *' into `struct server_context'

It didn't make much sense to parse the configuration values and load the SSL
keys on each connection.
Fix connection abortion
Implement irc_try_read()
Rename connection_abort() to connection_kill()
Implement irc_try_write()
Add a few token validation functions
Only compile regex's once
Initialize the server name
Apparently it's the "realname"
Add a strtoul() wrapper
Load an MOTD on start
Load X/Open message catalogs

This is going to enable making changes to ERR and RPL messages without
modifying the source code.

Localized messages could be interesting. :)
Put a prolog at the top of configuration files

Later I'm going to put in there some more information about the format etc.
Miscellaneous little things
Don't forget that channels have users
Add support for custom str_map key comp. fun.

That wasn't hard.