Remove OPEN_MAX

The OPEN_MAX macro in limits.h should not be there.  It claims to be the
limit on file descriptors in a process, but its value is wrong for that.
There is no constant value, but a variable resource limit (RLIMIT_NOFILE).
Nothing in the kernel uses OPEN_MAX except things that are wrong to do so.
I've submitted other patches to remove those uses.

The proper thing to do according to POSIX is not to define OPEN_MAX at all.
The sysconf (_SC_OPEN_MAX) implementation works by calling getrlimit.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>