[RFC] Add pthread_detach_pwd call.

[Ondřej Bílka]

Hi,

One of problematic parts of threading is working directory. As it is
global a changing it is problematic. Particulary when there is a third
party library that does this without multithreading in mind.

I got idea how users could fix this without much effort. It is that we
implement a pthread_detach_pwd call which will cause all subsequent
queries/changes in thread be resolved by using thread local variable.

Possible disadvantage is that this would make open/fopen more complicated.

Comments?