add signal handling and traceback support therein.
factor the runtime into architecture-dependent and -independent pieces.
ditto for the OS dependence.
SVN=124020
diff --git a/src/runtime/rt1_amd64_darwin.c b/src/runtime/rt1_amd64_darwin.c
new file mode 100644
index 0000000..fe92d0b
--- /dev/null
+++ b/src/runtime/rt1_amd64_darwin.c
@@ -0,0 +1,11 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "runtime.h"
+
+void
+initsig(void)
+{
+ /* no signal handler on mac yet */
+}
