Review changes:
  * tarantool_lua_load_startup was renamed to tarantool_lua_load_init_script;
  * TARANTOOL_LUA_STARTUP was renamed to TARANTOOL_LUA_INIT_SCRIPT;
  * init.lua int the test suite is optional now;
  * Additional comments was added.

Loading start-up Lua script 'init.lua' routine was moved to separate fiber. It
allows to avoid tarantool crash in case when 'init.lua' calls box.insert
(box.update, box.delete, etc...) procedure.

'init.lua' start-up file loading was moved from box.lua to tarantool
initialization section after main modules initialization (lua, mod, admin,
etc..). New tests for 'init.lua' was added.

Supporting 'init.lua' start up script was added to test suite.

Post-merge fixes: revert changes to libev configuration files.

Conflicts:
	mod/box/box.m
	test/box/admin.result

Conflicts:
	mod/box/box_lua.m
	test/box/lua.result
	test/box/lua.test
	test/box_big/sql.result

https://bugs.launchpad.net/tarantool/+bug/955226
Remove trailing spaces.

https://bugs.launchpad.net/tarantool/+bug/977026

Avoid race condition while wal writer is stopping but the wal writer thread
didn't have time to start working.

Only flush stdio buffer once when done processing
a bulk of requests. This avoids an unnessary syscall (write())
per request.

This reverts commit 8dc70aac.

Conflicts:
	test/box/lua.result

(https://bugs.launchpad.net/tarantool/+bug/972345)

Make sure we do not try to destroy uninitialized
mutexes in the snapshot thread.

Implement FIFO policy for the wal writer queue.

This patch introduces wal_mode configuration variable,
which can take either "fsync" or "fsync_delay" values.

In "fsync" mode, we open the write ahead log in O_SYNC
mode, and thus sync every write to disk.

Th fsync_delay mode is the backward-compatible mode:
in this mode, we only do fsync once every fsync_delay
seconds. If fsync_delay is 0, there is no fsync.

Otherwise, this patch is only adding auxiliary headers,
object files, etc.