include libc.h for bio.h; should always have been done.

Reference: /n/sources/patch/applied/rune5-libmach-libc
Date: Thu Apr 25 00:58:37 CES 2013
Signed-off-by: geoff@plan9.bell-labs.com

--- /sys/src/libmach/0.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/0.c	Thu Apr 25 00:58:16 2013
@@ -4,6 +4,7 @@
  * currently no compiler - not related to 0c
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "mips2ureg.h"
 #include <mach.h>
--- /sys/src/libmach/k.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/k.c	Thu Apr 25 00:58:16 2013
@@ -2,6 +2,7 @@
  * sparc definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "/sparc/include/ureg.h"
 #include <mach.h>
--- /sys/src/libmach/q.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/q.c	Thu Apr 25 00:58:16 2013
@@ -3,6 +3,7 @@
  *	forsyth@terzarima.net
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "/power/include/ureg.h"
 #include <mach.h>
--- /sys/src/libmach/v.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/v.c	Thu Apr 25 00:58:16 2013
@@ -2,6 +2,7 @@
  * mips definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "/mips/include/ureg.h"
 #include <mach.h>
--- /sys/src/libmach/68020.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/68020.c	Thu Apr 25 00:58:16 2013
@@ -3,6 +3,7 @@
  */
 #include <u.h>
 #include "68020/ureg.h"
+#include <libc.h>
 #include <bio.h>
 #include <mach.h>
 
--- /sys/src/libmach/alpha.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/alpha.c	Thu Apr 25 00:58:16 2013
@@ -2,6 +2,7 @@
  * alpha definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "alpha/ureg.h"
 #include <mach.h>
--- /sys/src/libmach/sparc64.c	Thu Apr 25 00:58:16 2013
+++ /sys/src/libmach/sparc64.c	Thu Apr 25 00:58:16 2013
@@ -2,6 +2,7 @@
  * sparc64 definition
  */
 #include <u.h>
+#include <libc.h>
 #include <bio.h>
 #include "sparc64/ureg.h"
 #include <mach.h>