libc: Add sys/fcntl.h for compatibility.

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

(cherry picked from commit e55151472b89067672e865858ccc2d2f28b91cd6)

Change-Id: I1eff872be589a5bcf9fd56077c71f8002c74fdaf
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>