Increase the ID field in the shmlog records from 16 to 32 bits to cater
for 64k+ connections.

Both varnishd and libvarnishapi needs to be recompiled, but apps should
not need to.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4264 d4fa192b-c00b-0410-8231-f00ffab90ce4