[rfc 0/4] fiber/stack: Increase stack size and shrink rss usage

[Cyrill Gorcunov]

Hi! This series tries to address a problem with stack overflow
on new distros. Please review carefully. It is still rfc because

 - need to wrap code with more ifdefs for systems where no
   madvise syscall present, which I address next once we're
   agreed on the patches;

 - need intensive testing where I could really use some help
   from more experienced developers since I've no clue how
   to cause stack exhausting from inside of lua script

 - actually I prefer to not use histogram here since it
   makes code even more complex, and I seriously consider
   moving stack processing into a separate file, say
   fiber-stack.cc or something

Anyway, please take a look once time permit. Comments are welcome!