fix the somehow newly introduced warnings

drivers/filter/md5.c

@@ -188,7 +188,7 @@ MD5Final (digest, ctx)
  * reflect the addition of 16 longwords of new data.  MD5Update blocks
  * the data and converts bytes into longwords for this routine.
  */
-static void
+void
 MD5Transform (buf, inraw)
      uint32 buf[4];
      const unsigned char inraw[64];

drivers/filter/optset.c

@@ -12,6 +12,7 @@
  *   May 2009 (D.C. van Moolenbroek)
  */
 
+#define _MINIX 1
 #include <stdlib.h>
 #include <string.h>
 #include <minix/config.h>