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.

Add comments, update the manual.

On snapshot, increase snapshot version id (u32),
save current snapshot version within a tuple.

On tuple free, check if tuple version is equal to current
snapshot id, if so do direct free, otherwise append tuple
to the delayed free list.

Fix https://github.com/tarantool/tarantool/issues/44

A copy-paste implementation of print(64 bit number)
used to add an extra newline at the end of printed string.

Allocate slab arena in shared memory to reduce pages splits during
snapshotting.
Adaptation of patch made by Yuri Nevinitsin @nevinitsin.