libc: Add sys/fcntl.h for compatibility.

Add a /usr/include/sys/fcntl.h file that includes <fcntl.h>.

Change-Id: Ie34bf7519607c5aae1fbea7c7dca249c9b7801cc
diff --git a/libc/include/sys/fcntl.h b/libc/include/sys/fcntl.h
new file mode 100644
index 0000000..cd30455
--- /dev/null
+++ b/libc/include/sys/fcntl.h
@@ -0,0 +1 @@
+#include <fcntl.h>