Instead of populating Lua box.space[] table once at
server start, update it with space data whenever it changes.
This is a pre-requisite patch for the new data dictionary,
which allows adding/dropping spaces on a running server.

Generalize session triggers to be usable for on_commit/on_rollback
events.

 * Parse request type inside of request_create
 * Remove palloc from request_create
 * Replace request_execute with a fun pointer in struct request
 * Refactor box_process API to accept struct request *
 * Create requests directly in iproto.cc and box_lua.cc
 * Update memcached, recovery and other parts to use new API

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.

Don't load corrupted tuples.

g++ (not gcc) works correctly when dealing with
extern __inline and __extern_inline constructions, thus
this hack is not necessary now.

Code review of cjson branch by Dmitry E. Oboukhov.
Hand-picking the changes since the original branch
is based on import of lua-cjson into Tarantool
revision tree, and this branch is based on a git
submodule.

This patch implements
https://blueprints.launchpad.net/tarantool/+spec/lua-cjson