Makefile: fixed path to kamailio.default in deb specs dir
mangler: fix double definition of contact_flds_separator, reported from ld
memcache: fix "maybe used uninitialized" warning from gcc
memcached: port to more recent memory manager callback structure

* port to more recent memory manager callback structure
* add small wrapper for calloc, implemented not optimal at the moment
  because the pkg_calloc from core/mem is not exported yet
* add initial code to check for server connection during startup, not
  enabled yet as its work in progress
* reorder structure a bit to allow for clean shutdown because of internal mm