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/Android.mk b/libc/Android.mk
index 0923939..bcb4afc 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -159,6 +159,7 @@
     bionic/libgen.cpp \
     bionic/link.cpp \
     bionic/locale.cpp \
+    bionic/lockf.cpp \
     bionic/lstat.cpp \
     bionic/malloc_info.cpp \
     bionic/mbrtoc16.cpp \