Add an initial implementation of pthread attributes for:
* detach state (joinable, detached)
* schedule params (just priority)
* guard page size (as skeleton) (requires kernel support maybe?)
* stack size and user-provided stack location (4 or 8 MB only, must be aligned)
Add some tests too, to the thread test program.
Also, LibC: Move pthread declarations to sys/types.h, where they belong.
This patch adds these API's:
- pthread_mutex_init()
- pthread_mutex_lock()
- pthread_mutex_unlock()
No mutex attributes are supported yet, so we only do the simplest mutex
wihout recursive locking.
It's now possible to block until another thread in the same process has
exited. We can also retrieve its exit value, which is whatever value it
passed to pthread_exit(). :^)
