This patch adds an include file <libc-lock.h>.  This simplifies
backports because upstream moved <bits/libc-lock.h> to this file in
commit ec999b8e5ede67f42759657beb8c5fef87c8cc63 (Move bits/libc-lock.h
and bits/libc-lockP.h out of bits/ (bug 14912)).

diff --git a/include/libc-lock.h b/include/libc-lock.h
new file mode 100644
index 0000000000000000..1f2fd8433454e870
--- /dev/null
+++ b/include/libc-lock.h
@@ -0,0 +1 @@
+#include <bits/libc-lock.h>