gnrc/tcp : Update documentation
gnrc/tcp : Update documentation

Add compile time parameters to doxygen group 'net_gnrc_conf'

OlegHahm/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,basilfx/RIOT,OlegHahm/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,basilfx/RIOT,miri64/RIOT,kYc0o/RIOT,OlegHahm/RIOT,jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,authmillenon/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,miri64/RIOT,basilfx/RIOT,OlegHahm/RIOT,ant9000/RIOT,miri64/RIOT,OTAkeys/RIOT,miri64/RIOT,kYc0o/RIOT,basilfx/RIOT,OTAkeys/RIOT,kaspar030/RIOT,authmillenon/RIOT,authmillenon/RIOT,OTAkeys/RIOT,ant9000/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,kaspar030/RIOT,authmillenon/RIOT,OTAkeys/RIOT,kYc0o/RIOT,authmillenon/RIOT,jasonatran/RIOT,kaspar030/RIOT,ant9000/RIOT,RIOT-OS/RIOT,basilfx/RIOT,authmillenon/RIOT