Fix compiling errors on windows platform
Fix compiling errors on windows platform

It looks like symbol 'interface' is predefined somewhere and makes
compiler confused.

abhinavdangeti/memcached,owendCB/memcached,cloudrain21/memcached-1,mrkwse/memcached,couchbase/memcached,abhinavdangeti/memcached,abhinavdangeti/memcached,owendCB/memcached,cloudrain21/memcached-1,daverigby/kv_engine,jimwwalker/memcached,daverigby/kv_engine,Metaswitch/memcached,couchbase/memcached,cloudrain21/memcached-1,Metaswitch/memcached,daverigby/memcached,abhinavdangeti/memcached,daverigby/kv_engine,Metaswitch/memcached,jimwwalker/memcached,abhinavdangeti/memcached,Metaswitch/memcached,cloudrain21/memcached-1,Metaswitch/memcached,mrkwse/memcached,daverigby/memcached,mrkwse/memcached,daverigby/memcached,jimwwalker/memcached,owendCB/memcached,owendCB/memcached,couchbase/memcached,mrkwse/memcached,daverigby/memcached,daverigby/kv_engine,couchbase/memcached