From: Arjan van de Ven <arjanv@redhat.com>

Do flex mmap for x86-64.  mmaps will grow down in the address space now
instead of up.

Patch has 2 parts; the generic strategy selection, and code to make a correct
TASK_SIZE .  the later may be fixed in your tree already in which case it's
redundant.  

Modified by AK to apply to 64bit processes too.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>