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

Don't create an extra port_buf object, to process a request. Eliminate
obsolete wrappers, such as process_ro().

Call box_select() directly from iproto and Lua/C bindings,
bypassing process_rw entry point. Saves a few CPU cycles
and opens the path for further refactoring.

Remove one usage of box_process which we aim to eliminate.

* make sure long-run tests pass
* more systematic approach to downcasts to MemtxIndex in
alter/system spaces code

Support multi-part keys. Allow key duplicate
compaction. Reduce storage cost, encode metadata,
do not store msgpack (except value part).
Reconstruct tuple on read using index schema.

[replication]

JOIN support temporary put to not working
condition: there is no way to access possibly
deleted space schema during the operation
for a tuple reconstruction
(multi-thread).

recreate space key_def during join; enable join

sophia: make every operation asynchronous

sophia: fix join cursor and tests

sophia: implement delayed update operation

sophia: make delete write-only

implement Handler::executeReplace

sophia: merge fixes

make upsert operation an engine specific

sophia: make update logic common to memtx

sophia-integration: switch to Sophia v1.2.3; implement upsert

sophia: add half_commit mode support

This mode disables conflict resolution for
'prepared' transactions and solves the issue with
concurrent write-write conflicts during wal write/yield.

sophia: do not allocate tuple during replace or update; refactoring

sophia: extend and reorganize test suite

sophia: implement box.sophia()

sophia: #681: support or produce error on space::alter

sophia: extend recover tests

sophia: add separate iterator tests

box: enable per-engine select

    * add executeSelect() into engine handler API
    * add MemtxIndex; move preallocated m_position from Index to MemtxIndex
    * remove it->close()
    * remove IteratorGuard class

    note: Sysview and Sophia engines yet share the same select code in
    engine::executeSelect() (which does iterator alloc-free)

box: remove close call from box_iterator_free()