Defining int errno; resuls in the following error on amd64:

  ld: errno: TLS definition in /lib64/libc.so.6 section .tbss mismatches
  non-TLS reference in main.o

Patch by Alex Efros:

  http://code.swtch.com/plan9port/issue/39/
--- plan9/src/cmd/9660srv/main.c
+++ plan9.new/src/cmd/9660srv/main.c
@@ -38,7 +38,7 @@
 uchar mdata[Maxiosize];
 char fdata[Maxfdata];
 uchar statbuf[STATMAX];
-int errno;
+#include <errno.h>
 
 
 extern Xfsub	*xsublist[];