Allow disjunctions in SELECT WHERE clause and LIMIT
clause in SELECT, to be able to cover the problem
reported in Bug#729758.

Fix a bug with prepare_gdb arguments (remove an extra
space in -e option).

Add a simple test for Bug#729758.

The following bugs were reported in the process:

Bug#729789 "Zero limit is treated the same as no limit"
Bug#730593 "Bad data if incomplete tuple"
Bug#730613 "SELECT with a disjunction on multiple keys returns
matching tuples twice"

Implement a number of simple fixes to compile on FreeBSD:
- work correctly with a GCC version that doesn't have
  -Wno-unused-result
- compile even if not GNU libc
- tee doesn't have '--append' option on FreeBSD, use
  the short version ('-a').
- fix a typo in log_io.c, ENOENT, not ENONET.

Bug#712447 "Valgrind reports use of not initialized memory
after 'reload configuration'

Bug#695689 "'save snapshot' does not report error when it occurs"

Bug#686411 "Possible data loss when renaming a snapshot"

Implement
https://blueprints.launchpad.net/tarantool/+spec/tarantool-test-runner.

This commit adds an implementation of test running framework
(test-run.py), and a simplistic interactive client for
the administartive console of tarantool (admin.py).

A prototype of the first test suite is added in
directory test/box.

"run" is a convenience symlink to test-run.py.

This commit also adds "make test" goal to the
top-level makefile.