Remove SO_REUSEADDR from ipsocket_t

Add unit test to check for error EADDRINUSE.
This prevents port hijacking.
In the future SO_REUSEPORT (socket option) will be supported
to allow multiple processes to listen as network deamon on
the same TCP port.
Implement logurl_ipaddr

Function void logurl_ipaddr(const ipaddr_t * addr, const char * varname, uint8_t logchannel);
logs addr as "varname: udp://ip:port\n" or "varname: tcp://ip:port\n"
Implement daemonize_process

The function daemonize_process replaces initdaemon_process.
The difference is that daemonize_process makes the calling
process a daemon process whereas initdaemon_process created
a new process running as a deamon.

This allows the runnig process to become a daemon without
creating another process. Internally fork() so
daemonize_process creates a child process and ends the caller.
But the it appears as if the caller is daemonized.
Add target test to Makefile

The command "> make test" runs all compiled unit tests in »Release« mode.
The run executeable is »bin/unittest«.