Implement a generic inter-cord communication bus and use it
in separating network I/O and transaction processor.

Split all request processing work into network thread part
and transaction processor thread part, and make these
parts multi-threading safe.

Generalize fiber pool into an own data structure and API.

Misc cleanups.

This patch adds `src/module.h` header file with definition of all public
API functions suitable to use in Lua/C modules for Tarantool. This header
is automatically generated from src/*.h by CMake (`make generate_module_api`)
by extracting code blocks between /** \cond public */ /* \endcond public */
Doxygen-style comments.

Definitions of functions in module.h are frozen and must not be changed by
future commits/releases. A new test case `app/module_api` is added to check
compilation, linkage and loading of Lua modules and functionality of
provided API functions.

Other changes:

 * Convert mysql and pg to use module.h and prepare to convert to .c
 * Fix includes in say.h, coeio.h
 * Rename luaL_pushnumber64 to luaL_pushuint64 and
          luaL_pushinumber64 to luaL_pushint64
 * Add LUA_API macros to public luaL_* functions (actually adds extern "C")

libcore is a thick a thick bundle with almost everything.
Rename it to libserver.

Extract the minimal server core with fibers & exceptions into libcore.

Add a prototype unit test for fibers.

Provide fine-grained keepalive options on Linux, which
supports per-socket defaults.

Fix a bug with trying to set keepalive options for UDP
sockets - don't try to do it.

 * Split parser and resolver in src/uri.rl
 * Extend URI parser grammar to fully support RFC3986
 * Add Lua bindings to URI parser
 * Implement proper DNS logic in coio_connect() /
   evio_service_bind()
 * Replace uri_to_string() with sio_strfaddr()

Prerequisite for #447

No test case since we don't test contents of the log in 1.5.

Use underscores instead of dashes in file names.
Use 0 for success -1 for error.

Update code and tests.

This patch explicitly saves Exception to a thread-local variable inside
struct cord on tnt_raise(). This variable can be used to safetly
re-throw last exception from any place (not only from catch() block).
This technique requires exception to be thrown and catched by pointers.
tnt_raise macros was rewritten and all 'catch (Exception &)' blocks were
substituted with 'catch (Exception *e)'.

This patch also adds a new feature to box.raise() function.
When called without arguments box.raise() re-throws last exception (if
any).

These changes needed to implement proper handlings of exception for FFI
calls.

address detection to sendto.

Inline bio_socket_close().
Don't allow connect/bind on a non-empty socket:this is error-prone.
Don't allow connect/bind on a socket which
is already connected/bound/used for something else.
This is error-prone.
Move bind_addrinfo to evio layer.
Don't create iobuf without need. In close(), set iobuf to NULL.
Timeouts are not exceptions. Merge _timeout and other calls in coio.

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.

Get rid of an artificial wrapper around libev's ev_io object.
This allows for more code reuse.

Make all subsystems (administrative console,
replication, memcached, binary protocol) use exception-based
socket API (sio.m).

Remove all fiber members related to socket I/O.
Remove fiber->peer and fiber->cookie.
The idea of the cookie is to preserve in the WAL
the originator of the request. This information is, however,
lost when saving a snapshot. To my knowledge there is no use
of this functionality, apart from pretty-printing
the WAL.

Peer is like cookie, but is textual and is used
for logging. However, now, as long as network errors
occur outside fiber context, most of the usefulness
is lost. The only remaining case is when someone is
trying to execute a write request on a read-only port.

For all other cases, sio.m already supplies SocketError
with peer name, and this is where it's most useful.

Introduce two levels of new API: sio.h (the basic
socket IO) and evio.h (libev integrated socket IO).

Start changing the code base to use the new API.
Begin with replication.m.