[PATCH 2/2] lib/core/fiber: Allow to extend default stack size

[Cyrill Gorcunov]

On Mon, Apr 01, 2019 at 11:51:09PM +0300, Konstantin Osipov wrote:
> 
> I don't think we should bother with making sure the stack is right
> for all fibers. You set the stack size, then you start fibers
> which depend on it.

Kostja, "require('fiber').cfg{stack_size=value})" implies that
lua read and parse it, but lua *itself* runs inside a fiber where
we've the stack size already allocated and what is worse its size
is compiled in. Next time when "readline" developers increase *own*
stack size we hit the same bug. Users simply won't have a chance to
run tarantool, instead they will have to wait us to increase default
stack size and rebuild the program.