slab_class was an ambiguous name, get rid of it.
Minor cleanups in salloc.m (prepare for refactoring).

Move third_party library compilation to the top level (less
directory traversal).
Provide an option for using system LibEIO/libobjc.

Enforce a naming convention for cmake/ scripts
(Find* and Build*).

Move ev and eio wrappers to third-party (todo: delete
them completely).

There is one (known) problem with this patch:
tarantool --version now prints incorrect compile flags.
To be fixed in a separate patch.

Since connect/disconnect events in iproto run outside
fiber context, queue execution of on_connect/on_disconnect
triggers through the request queue. Generalize the request
queue for that purpose.

Implement a framework for on_connect/on_disconnect triggers
and Lua bindings for it.

Add tests and docs.

Move Box API declarations to box.h.
Make box.h a public header.
Add comments to box functions.
Rename fuctions accordingly.
Make includes for connector/c more local.

This reverts commit cf093c0b.

Conflicts:
	src/box/index.h
	src/box/index.m

Reviewed-by: Konstantin Osipov <kostja@tarantool.org>