fiber-big-bada-boom: rewrite fibers module

 * Completely remove the call stack and schedule all fibers via libev
 * Forbid all invalid state transitions and implement FSM explicitly
 * Rework API to be like Lua coroutines (see fiber_resume/fiber_yield doc)
 * Rename fiber_yield_timeout to fiber_sleep, move infinity constant from ipc.h
 * Replace old fiber_yield calls by new fiber_sleep with infinity timeout
 * Replace old fiber_yield_to and fiber_call by new fiber_resume/fiber_yield
 * Add the support for passing and returning arguments on the stack (va_list)
 * Replace fiber_setcancellable(false) with @try ... @finally block in ipc
 * Remove fibers cache from iproto (duplicated fiber.m functionality)
 * Update comments && documentation (partial)
 * Add an unit test (partial)

Bugs fixed:
 * Bug#1082377 "test/box/lua.test is broken on box.fiber.resume()"
 * Bug#1099552 "box.fiber does not detect reused fibers"
 * Bug#1100875 "box.fiber.yield wake up caller on next event loop"
 * libev events do not resume cancelled fibers anymore (fixes WAL bug and other)
Fiber hooks (initial implementation)
Fiber Local Storage (initial implementation)
Merge branch 'fiber-local-storage'
Merge branch 'fiber-big-bada-boom'

Conflicts:
	include/fiber.h
	src/fiber.m
Merge branch 'fiber-hooks'

Conflicts:
	include/fiber.h
	src/fiber.m