Set signal handler for all signals, not just SIGTERM.
Print signal name to the log on exit.

Add constants for signal count. Rename. Coding style.

Do not use atexit() handlers, except the global tarantool_free()
function, which does nothing in the snapshot process.

Use check_symbol_exists(), not check_function_exists(),
to discover fdatasync(), since apparently on some BSD systems
the symbol is present in the library but not in the headers
(I hope not vice versa).

Don't use check_prototype_definition, since it's not available
in CMake 2.6.

Remove get_socket_addr(), use existing sockaddr_in
to save in the cookie.

Tuples are got a big bigger with shared-arena patch (4 bytes
per tuple overhead).

So we exhaust the current arena in out-of-memory test a bit
faster than before.