First, send a snapshot to the slave, and only then register
the slave with the cluster.
Misc cleanups.

Conflicts:
	src/lua/init.cc
	test/box/lua_sandbox.result
	test/box/lua_sandbox.test

Fix a bug when the server would enter read-write mode prematurely
in hot standby mode, and let the script continue and try to create
spaces/indexes.

The bug is a regression introduced by the patch which changed cfg.listen
to a dynamic option.

This is an *incompatible* change: box.cfg{} used to return before binding
to the primary port, this is no llonger the case.

Always bind to the listen port in box.cfg{} call, not in the background,
and leave local hot standby mode *before* leaving box.cfg{}.

This avoids tons of tricky race conditions in user scripts when box.cfg{}
has ended but the server is actually still read only. Except, thanks to
another bug in box_set_cluster_id(), it wasn't really read-only, because
box_set_cluster_id() would switch off read-only mode before local hot
standby has ended (so a superposition of two bugs).

The manifestation of this  was as follows:

Imagine the following script:
    box.cfg{listen = 3301}
    box.schema.space.create('tester')
    box.space.tester:create_index('primary')

The server would start in local hot standby mode. Save a snapshot.
Fall through to DDL. Then leave local hot standby and turn on
WAL. The created space will end up not being in the write
ahead log.

The problem wasn't noticable in most cases, since the server could
bind to the primary port quite quickly.

Fix the test runner to detect a local hot standby server as started.

Add a workaround for gh-721 until a complete patch is ready.

Fixed version of fiob must work on all platforms.

Conflicts:
	CMakeLists.txt
	src/fiob.c

Rewrite replication to use cooperative I/O.
Propagate replication exceptions to the main thread.
Introduce a function which stats a thread with a running
event machine in it.

Fix a few bugs related to destruction of resources allocated in a
non-main thread.

Remove replication_prefork() and all the code related to pushing
a socket into another process.
Add debug asserts to slab cache, to ensure it's used from a single
thread only.

open(, O_CREAT | O_DIRECT, ) creates a file and then fails with
EINVAL in case if the underlying filesystem doesn't support O_DIRECT.
This behaviour is stupid and unexpected.

Export memsize() in Lua (part of the original patch by @unera).

Conflicts:
	src/lua/bsdsocket.lua
	test/box/bsdsocket.result
	test/box/bsdsocket.test