Needed for Fedora buildbot

Reproduced on Fedora buildbot

No longer necessary after #1217 was fixed.

* Inline vclock_dup() (move allocation and deallocation to xlog.cc)
* Refactor xdir_index_file() to remove useless try-catch block
* Ignore panic_on_error in case of OOM
* Add missing include "exception.h"
* Remove artifacts

Conflicts:
	third_party/sophia

Incompatible changes: server is not removed from box.info.vclock anymore
on delete from _cluster. A new replica re-uses previous server_id and
also last known LSN (was only server_id, but LSN always started from zero).

A prerequisite for #1219 test case.

Conflicts:
	.gitmodules

Conflicts:
	.gitmodules
	client/tarantool/tc_print.c
	src/lib/small

move tarantool/sophia to tarantool-1.6 branch