Implement box.tuple.unpack(), which converts the tuple
to a list of lua atoms.

Add basic support for splice in box.update() operation.

Creating a new userdata object whenever a fiber is accessed
is inefficient and complicates fiber garbage collection:
if a fiber is referenced to by multiple userdata instances,
it's hard to know when to free it up. Implement
'memoize' pattern for fiber userdata to deal with
these two issues.

After this patch, no matter how and where from
one gets a reference to a fiber, it's the same
userdata object.

As a side effect, getting fiber identity in Lua
is also easy -- one can just directly compare two
fibers to tell whether or not they are the same.

Add fiber.cancel(), fiber.sleep(), fiber.testcancel(),
fiber.id().
Draft the fiber library interface description.

Update ER_NO_SUCH_PROC, if the procedure doesn't exist,
quote the procedure name, since it can be empty.

Check that --background actually works, fix
the coding style.

A fix and a test case for
https://bugs.launchpad.net/tarantool/+bug/750658

--background neither closes nor redirects stdin/stdout/stderr

--background option didn't work properly, since stdin/stdout/
stderr streams were left open and pointing to a terminal.

This lead to a hang when tarantool was started from a
shell script or over ssh.

If --background option is given, we need to fork,
try to create a pid file, close stdin/stdout/stderr
and then initialize the logging
subsystem.

Add tuple::pairs() and tuple:next() implementation.

Update tuple metatable __index implementation to do
method lookup.

Fix a bug in box.unpack() where we wouldn't check that
lua_tolstring() can return NULL (which happens if nil
is on the stack).

Add tests.

Implement iterators, range select, namespace truncate.

yield function was renamed to fiber_yield.

Duplicate keys are sorted by tuple pointer value.
This led to non-stable test output when retrieving
all duplicates.
Sort results in the test runner to avoid sporadic
errors.

Simplify index_tree_el_compare
Make iterators usable regardless of index type.
Add coverage.

Add more tests.

In iterators over tree indexes, check
that key type matches field type.
Add tests for non-unique multipart keys.

Update output of the python test library
to not print extra trailing '\0' at the
end of error message. Update test results.

Fix bug https://bugs.launchpad.net/tarantool/+bug/837315

When write_inbox() failed, wal_write() would throw
an exception.

This had two effects:
first, a call to confirm_lsn() would confirm lsn
of the failed transaction out of order (indeed, nothing
is written, so this lsn is confirmed before lsns
of transactions which are waiting on write to complete)

second, txn_rollback() was called with fiber->mod_data.txn == 0.

The second led to an assertion failure.

The fix only fixes the second effect, so that an error
is sent to the client, and the server does not terminate.

It's not possible to come up with a serial test
case for the bug, since to fill up all inboxes one
needs many concurrent writes.

Remove the restriction on type of primary key index.

Fix a compilation error.

Implement iterator over HASH index, and use it
in mod_snapshot() and build_indexes().

Change signature of index_tree_el_init, avoid
unnecessary use of palloc(), preallocate
buffers for reads and writes instead.