A dump task can be scheduled or completed after we saved stats.
Make sure this doesn't happen.

Closes #2696

Do not use thumb specifier for asm code, use unified syntax directive
instead.

Revoke permissions granted by the test.

Needed for #946

Relay reader fiber is jonable now and should be joined by relay main
fiber.
See #2284

Don't stop coio twice.

Update comments.

Replication slave send its current vclock to replication master
after recieving new data from master.
See #2284

There is a check in vy_point_iterator_apply_history that compares
statement's lsn with lsn with vlsn and skips history node if the
statement is invisible.

This check is wrong:
 - if TX was originally in a read view it could not read any
invisible statement.
 - if TX was not in a read view but were sent to read during yield,
the new created read view must see all current database state,
including data that was read by the iterator.
 - if TX is in read view and made some changes (in own TX write
set) it will skip TXW statement since it has INT64_MAX lsn.

Replace check with assert. Concern possibility of TXW statement.

Write appropriate test.

test/small symlink was created only on `make test`,
create this symlink `make all`.

Check current user write access on space truncate.

Fixes #2674

_truncate space write access is required for space truncation.
Add this privilege to bootstrap.snap.

See #2674

Closes #2609
Closes #2633
Closes #2616

Follow up #910

vinyl_cache_add takes pair of statements - current and previous.
By design, there must be no statements in cache between them.

Some time ago a check was made that the previous statement is in
cache and lays right next to current statement; if that was not
true, the function exited without building a cache chain.
The was wrong because there are some cases when the statement
could be removed by TX finalize/rollback after prepare or even by
cache garbage collector.

Later in this check 'return' was replaced by 'assert' and that
caused rare test crash.

Fix this check. Check only two things 1) absence of entries between
current and previous statements 2) presence of previous statement
if current is already in chain.

Add a test case.

See code comments for details.

Fixes #2685

Discard xlogs with large tuples after decreasing memtx_max_tuple_size.

Follow up #2667

Add a special dump-waiting error injection to vy_point_iterator_get
that will wait for a dump completion. Use it in test and make code
coverage complete.

In the point iterator test

Fix a couple of mistakes in point_iterator and enable it back.

Disable 'could be serializable' suggestion in tx_conflic test
since new point iterator adds its key to read set before reading
from disk and that leads to unnecessary conflicts sometimes.

Fix #2662

No semantic changes.

Follow up #2047

* Remove dependency on memtx from tuple_format_default
* Add tuple_new() to create standalone tuples
* Allow box.tuple.new() without box.cfg()

Closes #2047

Follow up the previos commit.

See #2667

- Use slab_get() as a fallback for smalloc() for large size
- Set MemTX slab_size to 16Mb and don't use memtx_max_tuple_size
  for calculation (Vinyl is not changed yet)
- Allow dynamic configuration of memtx_max_tuple_size

Closes #2667

Added options:

* verify_host - CURLOPT_SSL_VERIFYHOST;
* verify_peer - CURLOPT_SSL_VERIFYPEER;
* ssl_key - CURLOPT_SSLKEY;
* ssl_cert - CURLOPT_SSLCERT.

This patch adds ability to reload C procedures on the fly without
downtime. To achive that, Tarantool loads a new copy of shared
library and starts routing all new request to the new version.
The previous version remains active until all started calls
are finished. All shared libraries are loaded with RTLD_LOCAL,
therefore two or more copies can co-exist without any problems.
From now box loads all external modules via an unique symlink to
avoid caching inside dlopen().

If one of some module function is reloaded then all other functions
from this module will be reloaded.

Reviewed and heavily patched by Roman Tsisyk.

Closes #910

rbtree_next() has log(N) complexity to advance to the right subtree.
The new iterators saves the iteration path during descent.

Closes #1668

panic() from non-main thread calls exit(), which fires
at_exit triggers, which try to destroy TX data.

Closes #2686

Memtx checkpointing subsystem uses createReadViewForIterator and
destroyReadViewForIterator methods of Index. So these methods
are used only for ALL iterators before actual iteration starts.

 * no other cases of these methods using are covered by tests,
for example EQ iteration or using in the middle of iteration.

 * creation of general read view iterator is an overkill for
such a simple case as ALL iterator.

 * memtx read view iterators are incompatible with lazy lookup
and restoration patterns that are necessary for implementing
stable iterators.

Introduce new createSnapshotIterator method that would create
a special iterator for checkpointing and remove misleading
createReadViewForIterator and destroyReadViewForIterator methods.

Make memtx tree iterator lookup lazy - in the first 'next' call.
It makes the iterator similar to vinyl in case when a new tuple
is inserted between a moment of iterator creation and a moment
of first tuple retrieval. Make the inserted tuple visible to
the iterator.

Store last returned tuple in the iterator and if the tree is
changed between iterations - search for the stored tuple and
continue iteration from the found position. This will make the
iteration stable and every next iteration will return proper
(next or previous) tuple.

Fix #1796

Originally bps_tree had only lower/upper_bound methods for
retreaving iterators by given key.

Sometimes it is necessary to find an iterator position by a value
that is (can be) stored in a tree.

For example memtx tree index holds a bps_tree with
(struct tuple *) values and (const char *) key.
lower/upper_bound methods used (const char *) as an argument,
but for stable iterators we need to find a position in the tree
by (struct tuple *) value.

Implement bps_tree methods that will allow to find an iterator
by a value (element) in the tree.

Needed for #1796

Move memtx_tree_compare_key definition to header file to allow
compiler to inline it.

Get rid of memtx_tree_comprare wrapper, use tuple_compare instead.

Comment the code.

xlog is used from Vinyl and Lua. Convert this library to C just for
sanity.

Closes #2335

* Move XlogError to error.cc
* Move XlogGapError to recovery.cc
* Replace tnt_error() with diag_set()
* Remove scoped_guard from xdir_scan()

A part of #2335

Update test results (changes not committed in scope of gh-2663).

Add a configuration option to configure the number of EIO worker
threads. Default value is 4.

Fixes #2663

Follow up the previous commit

See #2678

Fix regression after 9b811605

Closes #2678