Author: Aleksey Demakov <ademakov@gmail.com>
commit 4511500afd3d4682dd5de6b4c21ddeb398556cac
commit ce16851dc9edfdca8c05f3786806a59aff450343
commit 67ea5c0b715e53e367ffffc201eb3285652a617c

Move the  block with @finally into an own function.

Implements
https://blueprints.launchpad.net/tarantool/+spec/fiber-specialization

After this patch, all requests even within the same session
are handled asynchronously, and responses are sent to the client as
soon as they become ready, regardless of the request position
in the input buffer.

This also changes  the internal implementation of iproto
from a "one fiber per connection" pattern to "fiber work crew"
pattern. This approach significantly reduces the amount of
context switches between fibers.

There is a bug in gcc Objective C support and nested exception,
with which an exception passes by a @catch clause if
there are nested @finally clauses. This patch doesn't work
around this bug, so if the server is compiled with gcc and
the client closes its side of the socket without fully reading
the input, the server terminates. The server needs to be compiled
with clang for now to work around this bug.

Do not modify output buffer between yield points:
in net-split, multiple fibers work on the same
session, and append output to the same output
buffer.

Fix argument getpeername

Change sio_advance_iov to never modify iov vector in place.
This allows for reuse of this function in a raw event
loop, without fibers.

Minor cleanups.

Make memcached/noreply.test less race prone:
flush all command is running in the event loop, and sometimes
it doesn't get a chance to finish before we issue the next
command.

Use a large timeout value to indicate an infinite timeout,
not 0. Chris J. Date teaches us that using 0 as a special
value of infinity is a bad idea.

An incomplete fix for a bug when a channel is destroyed
in atexit handler, but has fibers blocked on it.

Minor cleanups.