Introduced the bare minimum of ibuf accessors, which make
external merger possible:
- box_ibuf_reserve
- box_ibuf_read_range
- box_ibuf_write_range

Part of #5384

Msgpuck functions mp_snprint() and mp_fprint() now support
customizable MP_EXT serializer. This patch makes them able to
correctly serialize all tarantool's MP_EXT extensions: MP_DECIMAL,
MP_UUID, MP_ERROR.

Closes #4719

Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Serge Petrenko <sergepetrenko@tarantool.org>
Reviewed-by: Nikita Pettik <korablev@tarantool.org>
Reviewed-by: Alexander Turenko <alexander.turenko@tarantool.org>

 * sys/prctl.h can be found only on Linux, but cmake recognizes Debian/kFreeBSD
 as Linux.
 * extern "C" for TIMEOUT_INFINITY (it is used in plugins)

 * sys/prctl.h can be found only on Linux, but cmake recognizes Debian/kFreeBSD
 as Linux.
 * extern "C" for TIMEOUT_INFINITY (it is used in plugins)

Move third_party library compilation to the top level (less
directory traversal).
Provide an option for using system LibEIO/libobjc.

Enforce a naming convention for cmake/ scripts
(Find* and Build*).

Move ev and eio wrappers to third-party (todo: delete
them completely).

There is one (known) problem with this patch:
tarantool --version now prints incorrect compile flags.
To be fixed in a separate patch.

End the copyright madness. Tarantool authors maintain a shared
copyright on the code base. Remove individual copyright (c) from
specific files and put a single AUTHORS file in the project top.

tarantool_ev.m doesn't have to be an Objective C file,
since it's only a wrapper around C file ev.c.

Port tarantool to ObjectiveC.
Implement basic TNTException class and
 TNTFiberException and TNTBoxException subclasses.
Replace longjmp/setjmp with ObjectiveC exceptions.

mod/box: Restructurize request processing in the following way:

	try
		begin
		dispatch
		commit
	catch
		abort

where any error during request processing generate an exception.

Use CMake to:
- Compile tarantool_silverbox, tarantool_feeder.
- enable ./test-run testing out-of-source
- implement Debug/Release configurations
- add ENABLE_BACKTRACE ENABLE_TRACE and HAVE_BFD switches
- support auto-generated targets