Initial import of libcouchbase, version 2.0.3.

libcouchbase is a callback oriented client which makes it very easy to
write high performance, thread safe programs.

Package provided by Trond Norbye (upstream author) with some minor changes
from me.
Import cityhash-1.1.0 as wip/cityhash.

CityHash provides hash functions for strings. The functions mix the input bits
thoroughly but are not suitable for cryptography.