include libc.h

Reference: /n/atom/patch/applied2013/machvc
Date: Wed Jun 19 15:56:19 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libmach/v.c	Wed Jun 19 15:56:15 2013
+++ /sys/src/libmach/v.c	Wed Jun 19 15:56:16 2013
@@ -2,6 +2,7 @@
  * mips definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "/mips/include/ureg.h"
 #include <mach.h>