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/stdint.h b/libc/include/stdint.h
index a6f8505..a66e21e 100644
--- a/libc/include/stdint.h
+++ b/libc/include/stdint.h
@@ -29,8 +29,8 @@
 #ifndef _STDINT_H
 #define _STDINT_H
 
+#include <bits/wchar_limits.h>
 #include <stddef.h>
-#include <machine/wchar_limits.h>
 
 typedef __signed char __int8_t;
 typedef unsigned char __uint8_t;