[patch] specify entries not subject to LRU at write time

[Paul G]

folks,

i've put together a small patch (in fact, most of it is autoconf stuff) to 
allow writing 'permanent' items which won't be subject to LRU replacement. 
this is useful (i think) if you want to guarantee that some data survives 
either until its expiration or until the server/machine it's on dies. while 
this is obviously doable with the appropriate command line switch, this 
patch allows it to be specified on a per item basis and changed at any time, 
meaning you can store them in the same memory pressured memcached instance 
you're hammering with everything else.

testing and comments from memcached hackers wrt what i've subtly broken with 
this  would be most welcome. please note, while it works in my tests (such 
as they are), i *don't* guarantee that it won't eat your children or sleep 
with your wife ;)

usage:
  apply diff, autoconf + autoheader, then
 ./configure --enable-perm-items

(i've tried to make it as simple to try out as possible, admittedly so i can 
get some testing and comments on it).


for other options and a few short notes on the why/what/how, check the 
included README.

you can grab it here: 
http://www.perforge.com/permitems-patch-memcached-1.2.1.tgz

cheers,
-p