msg: prefetch data when doing recv()

Since that when we're reading the header we do lot's of small IOs, we
can really benefit from doing bigger reads.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
Simple Client/Server/Dispatcher

This commit implements an simple bi-directional
communications example using SimpleMessenger, a
new SimpleDispatcher Dispatcher subclass, and new
address helpers.

A new CEPH_GENERIC_SERVER entity type and support for
communication with generic servers is added.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>

Conflicts:
	src/CMakeLists.txt
simple_{server,client}: modify tool

make client wait for server responses

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
messenger: some prefetch fixes

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: cache decoded user info

Instead of accessing the raw user info data, cache the decoded
structure.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>