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 }.

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

A dropped user structure could still be accessed from sessions
which were authenticated with this user.

Check that a user is dropped when accessing it from the authenticated
session.

 + Add tarantoolctl enter instance_name command

This patch also changes box.info.server output for this case.

Avoid uncontrolled growth of region memory.

Stop producing "excessively sparse array"

Other changes:

 - "" or NULL=ffi.cast('void *', 0) now resets option to default value
 - app/cfg.test.lua converted to TAP format

Tarantool started to use getaddrinfo() to find suitable address for
binding both for IPROTO and CONSOLE ports. A hostname can be resolved to
various addresses families, depending on user settings. For example, all
moderns systems resolve 'localhost' to '::1' by default. This creates a
problem if one subsystem binds to '127.0.0.1' and some other tries to
connect '::1'. This patch unify hardcoded names and addresses in entire test
suite to use the same value. This is pre-requisite for #447, #368 and other
URI-related patches.

Other changes:

  * console.listen() now properly handles address arguments
  * console.listen() re-based on socket.tcp_server() code