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.
Thread::make_userspace_stack_for_main_thread is only ever called from
Process::do_exec, after all the fun ELF loading and TSS setup has
occured.
The calculations in there that check if the combined argv + envp
size will exceed the default stack size are not used in the rest of
the stack setup. So, it should be safe to move this to the beginning
of do_exec and bail early with -E2BIG, just like the man pages say.
Additionally, advertise this limit in limits.h to be a good POSIX.1
citizen. :)
MAXPATHLEN defines the longest permissable path length after expanding
symbolic links. It is used to allocate a temporary buffer from the buffer
pool in which to do the name expansion, hence should be a power of two.
On UNIX MAXPATHLEN has the same size as PATH_MAX.
