When selecting the next buffer to flush, take into account not
just its size, but how much of it has already been flushed.
This saves a couple syscalls per connection per event loop.

Replace socket('AF_UNIX', 'SOCK_STREAM', 'ip') with
        socket('AF_UNIX', 'SOCK_STREAM', 0).

Fixes distributions with missing "ip 0 IP" line in /etc/protocols
(e.g. Arch Linux).

 on memory fail there could be port->reply.found > 0 and uninitialized port->svp,
 that could lead to random error after svp restoration.
*) possibly fixed OPENTAR-97

closes gh-856

Rename global `fiber` into `fiber_ptr`

Rename global `fiber` into `fiber_ptr` (for use with gdb and avoidance of ambiguity with `struct fiber`)

Backport fix from tarantool/mysql by Anton Reznikov

Also fix :send() and :write()

Do not terminate the server on accept error.

This patch also fixes EINTR and EWOULDBLOCK handling for
socket:read() and socket:write() wrappers.

open(, O_CREAT | O_DIRECT, ) creates a file and then fails with
EINVAL in case if the underlying filesystem doesn't support O_DIRECT.
This behaviour is stupid and unexpected.