move Structrnd to runtime.h

R=ken
OCL=31125
CL=31125
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index b02844d..8f1cfa7 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -258,6 +258,11 @@
 	Amax
 };
 
+
+enum {
+	Structrnd = sizeof(uintptr)
+};
+
 /*
  * deferred subroutine calls
  */