Add Request object with method execute. Allocate
Requests on fiber->gc_pool. Clear txn from request data.
Make txn commit/rollback algorithm independent on the actual
request or request data.
Update valgrind suppressions with new call paths.

Rename a global variable, which had too common name,
to avoid easy to miss bugs.

Continue cherry-picking refactoring ideas from txn-refine
tree.
We only needed to store txn in fiber because in port_lua
implementation we needed to access lua_State.
Instead of keeping this indirect dependency, pass around ports
explicitly.
On the same token, make ports Objective C classes:
this is necessary to make them stateful.
In port_lua state keep a pointer to lua thread, and allocate
a new port_lua instance on each lbox_process call.
The port is currently allocated on fiber->gc_pool
and never destroyed.

We needed to have txn_cleanup() only because a tuple
which was read in txn was used in fiber->io_vec.
Decouple txn and network I/O and make sure
we can commit/rollback txn whenever we like, regardless
of what is given to fiber->iovec.

@todo: perhaps we need to optimize performance
of port cleanup for big selects.

Rename classes in *.rl file.
Patch valgrind suppressions.

We don't use box_ prefix consistently, so don't use it at all.

Remove box_ prefix from box_tuple and box_txn.

Move out from box.m INSERT/UPDATE/SELECT/DELETE/CALL
implementation.

Cherry-picking code from txn-refine.
Remove an extra member in struct box_txn.
Rename txn->tuple to txn->new_tuple.

Fix bug https://bugs.launchpad.net/tarantool/+bug/990728
"box.space:truncate() is a CPU hog".

The old truncate algorithm would restart iteration
from the beginning to delete every tuple.
With HASH index it was especially slow, since
it would have to skip more and more empty slots
to find a non-empty slot for deletion.

Rewrite the truncate() to walk linearly
over all elements and delete them.

This works both with HASH and TREE indexes.

On the same token make truncate multipart-index
aware (was missed in multipart-pk patch).
Add a test for that.

To work with multipart keys efficiently,
implement tuple:slice(). A slice returns
a linear set of fields from a tuple.
Convenient to retreive a multipart key or
tuple tail. Document tuple:slice().

Convert box.lua to box.lua.c and compile it in.
Fix broken out-of-source build of luajit, by adding
a few more generated files to touch-nocreate rule.

Replacing salloc() with malloc() found a bug triggered
by multipart key patch:
we don't always check for key cardinality.

When the slab alloc arena is fully used, and we try to
truncate a space, we could crash, since

a) we never check return value of salloc()
b) we used to salloc() an iterator for truncate(), and
it would return NULL, and we would try to access it without a check.

The fix is:

- to throw exceptions directly from salloc()
- to not use salloc() for iterators, since we still should
be able to truncate a namespace when the slab alloc arena is
full.

'find' TreeIndex class member was fixed. Now allocate enough space for key_data.

Spelling fixes in the error message file.

Add more information to the error when key cardinality
doesn't match index cardinality in exact match.

Avoid server start/stop in box_big/hash.test (ugly,
but until we have named/dynamic spaces, which are already in the
pipeline, we should not make our test procedure slower).

Rename multipart-pk.test to tree_pk_multipar.test:
consistently use underscores, not dashes, in file
names.

(Unrelated) Recycle more error codes.

Make keyValue an inline function to save a few CPU cycles.

Avoid creation of an extra table in box.lua just to find out
variable list array cardinality.

Revert changes to box.update():
a) they break backward compatibility

This reason alone should be sufficient. There must be no changes
which break backward compatibility in a stable release, unless
it's a fix for a crashing/security bug.

box.update() changes got to be done in a separate task,
and should not break backward compatibility.

Leave update_ol for now, to test multi-part primary key updates,
even though the function itself is quite heavy, hardly something
we can recommend while running Lua procedures in production.

Warnings was removed. Minor coding-style cleanup.

'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.