The x86_64 a.out.h got a definition of STACK_TOP_MAX, which interferes with
the UML version.  So, just undef it like STACK_TOP.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>