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 }.

Fix some bugs in the function (now it uses libc's (3) dirname ffi.call).

closes #541

Merge branch 'stable'

Conflicts:
	test/box/bsdsocket.test

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