Closes #2754

Needed for #2754

sc_space_new return value always is unused. Make sc_space_new
return void.

Needed for #2754

Version is needed in #2754 to ignore space format,
if schema version < 1.7.6.

Needed for #2754

Needed to get format fields during alter in #2754

No semantic changes.

Needed for #2754

Needed for #2754

Needed for #2754

Needed for #2754

Minor renames

Travis images are broken by design.

Closes #2069

Ubuntu Trusty on Travis is buggy.

Fixes #2752

Needed for #946

If the iterator over a merge source was restored to a newer version of
the min key, we must not increment front_id, otherwise the source won't
be advanced on the next iteration, potentially resulting in the same key
returned twice by vy_merge_iterator_next_key(). In the long run, this is
likely to break the cache. Fix this and add an assert() checking that it
never happens.

While we are at it, remove loop from vy_read_iterator_merge_next_key()
that checks that the statement returned by vy_merge_iterator_next_key()
isn't the same as the statement returned to the user last time. The loop
condition should never evaluate to true, which is assured by the new
assert().

Fixes: 61ffe793 ("vinyl: fix read iterator restoration to a newer
version of the same key").

Throw error, if a new name for a fiber in Lua is too long.

Closes #2622

In case of an aggressive optimization coro_unwcontext might be inlined,
so it's should be good to add rax/eax to asm clobber list.

* remove obsolete comments from recovery.cc
* update example lua

* update tarantool man page
* cross-reference tarantool and tarantoolctl pages

The fallthrough attribute with a null statement serves as a fallthrough
statement. It hints to the compiler that a statement that falls through
to another case label, or user-defined label in a switch statement is
intentional and thus the -Wimplicit-fallthrough warning must not trigger.
The fallthrough attribute may appear at most once in each attribute list,
and may not be mixed with other attributes. It can only be used in a switch
statement (the compiler will issue an error otherwise), after a preceding
statement and before a logically succeeding case label, or user-defined
label.

https://developers.redhat.com/blog/2017/03/10/wimplicit-fallthrough-in-gcc-7/

Ubuntu Trusty on Travis is buggy.

Fixes #2752

Closes #2069

- Fix applier.cc/relay.cc dependencies. Relay/applier should not
  depend on box.cc. Add two separate flags to control timeout.
- Remove hardcoded REPLICATION_CFG_TIMEOUT.
- Fix replication_timeout value checking.

Follow up #2707

Signed-off-by: Roman Tsisyk <roman@tarantool.org>

Sometimes old relay instance couldn't be deleted yet before new
slave subscribe is there. For this case an invalid cfg error is
returned, and applier should reconnect after timeout.

Fixes #2277

Fixes #2707

Set applier reconnect delay and ack interval (hearthbeat interval) via
box.cfg replication_timeout parameter. Relay timeout (time interval
without hearthbeat messages) is four times bigger than replication_timeout,
so up to three hearthbeat messages can be skipped until connection to close.
Fixed #2708

After the read iterator selects the minimal key across all available
sources, it checks mutable sources for new statements using ->restore()
callback. If there is a new statement in a source, it uses it as the min
key provided it is *strictly* less than the current min key. If they are
equal, the min key isn't changed, but this is wrong, because the new
statement may be newer than the statement selected previously. If we
don't select it, we might end up with stale data in the cache. Fix this.

Since ->restore() is not used by the read iterator to start iteration
any more, we can remove the corresponding code from the cache iterator
->restore() callback. Although it might be tempting to simplify it even
more by doing a full lookup every time the cache version changes, as we
already do in case of memory and txw iterators, it doesn't seem to be a
sound idea, because the read iterator itself can change the cache
version on each iteration by inserting new elements into the cache, even
if there were no disk accesses.

We don't need to handle iterator restart in the ->restore() callback, so
we can remove the corresponding code. Also, let's reuse the start
iteration function for restoration, because the two cases are in fact
equivalent.