Fix xc_save compile

# HG changeset patch
# User [email protected]
# Date 1205173511 25200
# Node ID 3eef1d83c6edd4b82b18bb704b58d38127c07f65 # Parent 2700daff2d43f337801844599969bde83a7f76ed Fix xc_save compile

Add missing <err.h> include.

@@ -16,6 +16,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <err.h>
 
 #include <xs.h>
 #include <xenctrl.h>