added additional checks to /wal_off/snapshot_stress.test.lua

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

Replace socket('AF_UNIX', 'SOCK_STREAM', 'ip') with
        socket('AF_UNIX', 'SOCK_STREAM', 0).

Fixes distributions with missing "ip 0 IP" line in /etc/protocols
(e.g. Arch Linux).

socket method is writable(), not writeable().

In case output is multiplexed, obuf_rollback_to_svp could
roll back to a very early  in the output buffer, since
svp is taken before a possible yield.

This is a regression introduced in the patch which
removes iproto_port from Lua calls.

Test case

*)added proper cleanup
*)minor fixes and checks

vclock_get() can return -1 in this case.
Probably introduced by 311551f9

Push a workaround for infinite loop in backtarce_foreach() when
fiber == self: do not try to print trace of the current fiber.

Conflicts:
	src/iproto_port.cc

*) fixed potentionally unsafe code:
  on memory fail there could be port->found > 0 and uninitialized port->svp

 on memory fail there could be port->reply.found > 0 and uninitialized port->svp,
 that could lead to random error after svp restoration.
*) possibly fixed OPENTAR-97

finalizers.test marked as long run in suite

 *) added stress test for snapshotting
 *) moved finalizers.test.py to long_run

test-run udpated

set test-run module in gh-3 branch for review

closes gh-856

Conflicts:
	include/fiber.h
	include/mutex.h
	src/admin.cc
	src/admin.rl
	src/box/box_lua.cc
	src/box/request.cc
	src/box/txn.cc
	src/coeio.cc
	src/coio.cc
	src/fiber.cc
	src/ipc.cc
	src/iproto.cc
	src/log_io.cc
	src/lua/bsdsocket.cc
	src/lua/init.cc
	src/lua/session.cc
	src/memcached-grammar.cc
	src/memcached-grammar.rl
	src/memcached.cc
	src/recovery.cc
	src/replica.cc
	src/replication.cc
	src/say.cc
	src/session.cc
	src/tarantool.cc
	src/util.cc

Rename global `fiber` into `fiber_ptr`

Rename global `fiber` into `fiber_ptr` (for use with gdb and avoidance of ambiguity with `struct fiber`)