In order to get the __NR_* constants, we need sys/syscall.h.
linux/unistd.h works as well since it includes syscall.h, however syscall.h
is more parsimonious.  We were inconsistent in this, and this patch adds
syscall.h includes where necessary and removes linux/unistd.h includes
where they are not needed.

asm/unistd.h also includes the __NR_* constants, but these are not the
glibc-sanctioned ones, so this also removes one such inclusion.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>