Prompted by Dave Mielke: This adds a comment explaining why we do not
define _XOPEN_SOURCE, even though the pread man page says you should.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>