core: set TOS for IPv6 UDP sockets

- reported by Klaus Feichtinger, FS#179
snmpstats Add a few more TCP connection settings
snmpstats Adding another list of TCP settings

Just a few more to go, then TLS
modules/outbound: updated edge proxy example in README
snmpstats Adding more memory data variables

Also, remove dependency of the kex module by interfacing directly
with the core the same way as the kex module does get memory information.
Makefile: pure target associated to maintainer-clean
Makefile.defs: version set to 4.1.0-dev2
usrloc: use NULL domain for updating ul attributes for use_domain=0

- use counter var for db matching keys