Linux-specific option obsolete since kernel 2.2

Wait() no longer called hence waiters not initialized. Does it make
sence to have a test for :waiters (undocumented internals)?

- Waiting on a brand new socket (neither listen nor connect called)
  completes immediately with HUP status on Linux. However on FreeBSD/osx
  it never completes.

- Attempting to connect to a port bound on a loopback interface which is
  not yet listening yield ECONNREFUSED in blocking mode on Linux. On
  FreeBSD/osx blocking connect never completes ("never" means it doesn't
  complete in a reasonable time).

- Calling shutdown() on a listening socket works in Linux but in
  FreeBSD/osx it doesn't.

Note: it was incomplete, made thing unnecessary complex and it did not
align with the CMake way (c) for crosscompilation.

Pass sysroot on OSX.
Make the code in luajit.cmake a bit more sane and straightforward.

Note: v1 of this patch was reverted due to performance regression.

Update reference to the pure php client

This reverts commit 615f0985.

This reverts commit 3010b98b.

Document UPSERT in the protocol spec.

Build system fixes on osx, +misc.

Pass sysroot.
Abort build if preprocessing fails (a stage in tarantool.h generation).

Note: it was incomplete, made thing unnecessary complex and it did not
align with the CMake way (c) for crosscompilation.

Pass sysroot on OSX.
Make the code in luajit.cmake a bit more sane and straightforward.

We were passing -g flag twice, just uncool.

gh-1017 double-run bug fixed, and fixed same bug in stat_net. But bug with probability doesn't repeated

Make code in alter.cc less error prone and less verbose.
Miscellaneous cleanups.

Luajit comes with a custome buildsystem. Fixed passing custom
CC; it bites on FreeBSD since we are currently unable to build
with default CC (gh-786).

Issue was due to _Thread_local keyword used in the system
header which gcc4.8 fails to understand in c11 mode.
In --std=gnu99 mode it works.

Updated cmake test to claim no c11 support if ctype.h fails
to compile.

Conflicts:
	src/rmean.cc

Fixed a pair of minor bugs:
1)Fixed multidim_test, it could occasionally crash
2)Fixed rtree_misc.test.lua, snapshot test part
3)Reverted another rtree key mode -
  ind:select{0, 0, 10, 10} and
  ind:select{{0, 0, 10, 10}} - both works now