This patch implements show index and shows memory waste of the
slab allocator.

This patch also reworks title() to show role@custom_proc_title for all roles
as defined in the documentation.

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

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

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

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

 * sys/prctl.h can be found only on Linux, but cmake recognizes Debian/kFreeBSD
 as Linux.
 * extern "C" for TIMEOUT_INFINITY (it is used in plugins)

What happened in production, during upgrade:
- logger option in the config file was pointing to nowhere
- the server would start, unable to check that the child logger
process died prematurely
- the server would fork spawner process to spawn replication relays
- a replica would come in, asking for data
- the spawner would successfully spawn a relay but die on SIGPIPE
when trying to write to the log (a pipe leading nowhere by now)
about the event
-> we have a master with a dead spawner process, no more replicas,
sorry.

Well, someone should check their configuraiton in the first place.
Nevertheless, try to be nice, and:

- don't die on SIGPIPE in the spawner process.
- when starting the logger, make an effort to check that it has started
successfully. There is no reliable way to find this out, so do
it with the best effort.

Refactor space cache code, create indexes
in space_create().

Remove init_storage option.

Move struct key_def into an own header.
Rename key_def methods to follow the coding style.
Rename field_data_type to field_type.
Instead of panicking on key_def initialization
error, throw an exception.

The allocator consists of a common slab cache, region and slab
allocators.
The patch provides unit tests.

It also modifies rlist_shift to be more in line with the
rest of rlist functions.

Before introducing a stronger row handler API,
eradicate tbuf from log_io/recovery, and pass around
a pointer to row and row length instead.

- simplify the comparison function, only shortuct the single-part
  NUM key case.
- tweak mh_find() declaration
- remove wrappers around hash values
  and keys

Rename tarantool_pthread.h to tt_pthread.h

This is a pre-requisite for addition of Perl stored procedures.