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/wchar.h b/libc/include/wchar.h
index ea6aca0..0a94cee 100644
--- a/libc/include/wchar.h
+++ b/libc/include/wchar.h
@@ -36,7 +36,7 @@
 #include <time.h>
 #include <xlocale.h>
 
-#include <machine/wchar_limits.h>
+#include <bits/wchar_limits.h>
 
 __BEGIN_DECLS