Avoid overwriting tuple data with information necessary for
smfree(). Only use a single pointer to store delayed free context.
Add a test case.

Minor cleanups/comments/renames.

Fix box.schema.user.exists(nil) box.schema.role.exists(nil)
and box.schema.func.exists(nil) to return false (PeterG report).
Add tests.

Conflicts:
	test/box/cfg.result

Some settings (too_long_threshold) were not set at all
after the change that removed initialization of all options
from box_init().

Always set all dynamic options after load_cfg().

Refactor output of box.slab.info() to be more readable (as readable
as I could make it taking into account it's a Lua table).

Add comments. Make readahead dynamic as well.

1)Added 'slab_alloc_maximal' config option.
2)Tuple slab cache is creating now with a range of orders depends on
  'slab_alloc_minimal' and 'slab_alloc_maximal' config options.
3)Smallocator's mempools now selects proper order of slab depends on
   size of an object.
4)after CR fixes

Set missing trailing zero in find_path().

Rewrite snapshot_daemon to use fiber.channel() instead of
undocumented API.

Explicitly mark places which are unsafe for cancel.

Remove the snapshot in abort_checkpoint(). Use coeio_remove/coeio_unlink
bindings instead of coeio_custom().

2)minor fixes of load_cfg.lua

Everything is cancellable. In fiber_cancel() use fiber_wakeup()
instead of a direct call. This make cancel safe with
regards to wakeup() and timeouts: i.e. it's safe to cancel
a fiber which is waiting on a timeout or is about to get
scheduled.