Convert box.lua to box.lua.c and compile it in.
Fix broken out-of-source build of luajit, by adding
a few more generated files to touch-nocreate rule.

Replacing salloc() with malloc() found a bug triggered
by multipart key patch:
we don't always check for key cardinality.

Make the test more explicit.
Remove old/new config checking, which is currently pointless.

When the slab alloc arena is fully used, and we try to
truncate a space, we could crash, since

a) we never check return value of salloc()
b) we used to salloc() an iterator for truncate(), and
it would return NULL, and we would try to access it without a check.

The fix is:

- to throw exceptions directly from salloc()
- to not use salloc() for iterators, since we still should
be able to truncate a namespace when the slab alloc arena is
full.

This version of libev optimizes async events significantly.

Fix bug
https://bugs.launchpad.net/tarantool/+bug/983094
"Valgrind tests were broken by WAL writer patch"

Keep track of WAL files opened for write
in recovery

Extend atfork handler to clear the wals,
to avoid collision with reuse of recovery
to save a snapshot.

Move some WAL-specific configuration settings
from wal_class to recovery, to avoid layers
of indirection when doing RELOAD CONFIGURATION

Conflicts:
	mod/box/box.lua
	test/box/lua.result
	test/box/lua.test

tarantool_lua_dofile function was rewritten.

Fix brokken static compilation of the client (we'll have
to find another solution for Darwin).

Make snap_io_rate_limit and io_collect_interval dynamic.
Add a test case.
Update the user guide.

Review changes:
  * tarantool_lua_load_startup was renamed to tarantool_lua_load_init_script;
  * TARANTOOL_LUA_STARTUP was renamed to TARANTOOL_LUA_INIT_SCRIPT;
  * init.lua int the test suite is optional now;
  * Additional comments was added.

Fix bug https://bugs.launchpad.net/tarantool/+bug/988701
"Build with '-DENABLE_CLIENT=true' was broken'

Until
https://bugs.launchpad.net/tarantool/+bug/962848
"Compilation with extrnal LuaJIT broke with addition of FFI"
is fixed, don't try to compile with external LuaJIT.