Make reactor pull size configurable per xmemcached client object

At my current job we use xmemcached and usage scenario is to use xmemcached per cache usage as they point to different set of memcached servers. We want to have capability to set reactor pool sizes different for different clients.

Some data from load tests we performed.


No of Client Objects|Connections per Client|No of Reactors per Client|Throughput
------------------- | -------------------- | ----------------------- | ---------
8|1|2|151K
1|8|16|114K
1|1|16|200K