[PATCH] simplify ulimit implementation

[Roland McGrath]

sysdeps/posix is appropriate because it's implemented in terms of POSIX
interfaces.

It's bad to lose any functionality, though __UL_GETMAXBRK actually being
used seems a bit unlikely.  But it's easy enough to add it.  So I'd do:
First commit: move file verbatim to sysdeps/posix/.
Second commit: add __UL_GETMAXBRK to that implementation.
Third commit: remove sysdeps/unix/bsd/ file.


Thanks,
Roland