unix: add arm64/linux support

This incorporates generation script changes from
http://golang.org/cl/7143.

Files generated on Ubuntu Trusty.

Change-Id: I28cfa0993573e1b280c549a67f453c0fb01dee2f
Reviewed-on: https://go-review.googlesource.com/10038
Reviewed-by: Rob Pike <r@golang.org>

unix/mkerrors.sh

@@ -124,6 +124,14 @@ includes_Linux='
 #ifndef MSG_FASTOPEN
 #define MSG_FASTOPEN    0x20000000
 #endif
+
+#ifndef PTRACE_GETREGS
+#define PTRACE_GETREGS	0xc
+#endif
+
+#ifndef PTRACE_SETREGS
+#define PTRACE_SETREGS	0xd
+#endif
 '
 
 includes_NetBSD='