Define DEFFILEMODE and friends

Define the macros ACCESSPERMS, ALLPERMS and DEFFILEMODE.
These macros originates from BSD but has been available in glibc
for quite some time.

Change-Id: I429cd30aa4e73f53b153ee7740070cebba166c57

libc/stdio/fopen.c

@@ -31,6 +31,8 @@
  * SUCH DAMAGE.
  */
 
+#define __USE_BSD
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>