* fixed ip-down segfault

This reverts commit d77729c3.

* implemented logwtmp module
* implemented connlimit module
* implemented advanced shaper
* implemented MS-Primary-DNS-Server/MS-Secondary-DNS-Server attributes
* fix per-interface PADI limiting (pppoe)
* fix module load order
* fix "show sessions match" (cli)
* other bugfixes and improvements

implemented connlimit module which can be used to reduce system overload due to flood of connections

l2tp: add Vendor-Name attribute to SCCRP

* implemented named IP pools (radius Framed-Pool attribute)
* implemented logging to system logger (log_syslog)
* implemented ability to send cli commands via snmp
* implemented PADI limiting (pppoe)
* implemented simultaneous radius requests limiting
* various bug fixes and improvements