Box still have a global pointer to its recovery state.
This pointer must only be used from TX thread from main process.

This patch is pre-requisite for thread-based JOIN/SUBSCRIBE handlers.

Other changes:

 * Add box_atfork() and recovery_atfork() callbacks
 * Change signature of recovery_state->row_handler
 * Execute JOIN request via box
 * Remove r->join_handler callback from recovery subsystem

`_func' space recovered before `_user' and auth_token can't
be retrived during creating struct func_def.

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

Extract the non-failing parts of the original patch by Roman.
Make an attempt at finding why coeio_custom is crashing when
replication_source is changed quickly - no success yet.

Recognize -w --wrapper, and don't daemonize if run from a wrapper.

Duplicate log_fd to STDOUT_FILENO on say_logrotate()

See also 0a1780cb

Tarantool's signal handlers are now installed *before* executing
Lua script. libreadline doesn't install own signals anymore.
TTY is now clean up properly in all cases.

This patch also fixes possible problems with signal handlers
after daemonization via box.cfg { background = true }.