Implement POSIX lockf.

This has been requested a few times over the years. This is basically
a very late rebase of https://android-review.googlesource.com/45470
which was abandoned years ago. One addition is that this version has
_FILE_OFFSET_BITS=64 support.

POSIX puts this in <unistd.h>. glibc also has it in <fcntl.h>.

Bug: http://b/13077650
Change-Id: I5862b1dc326e326c01ad92438ecc1578d19ba739
diff --git a/libc/include/sched.h b/libc/include/sched.h
index 930dd7c..0b9235b 100644
--- a/libc/include/sched.h
+++ b/libc/include/sched.h
@@ -28,8 +28,8 @@
 #ifndef _SCHED_H_
 #define _SCHED_H_
 
+#include <bits/timespec.h>
 #include <linux/sched.h>
-#include <machine/timespec.h>
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS