move things out of sys into os and runtime

R=r
OCL=28569
CL=28573
diff --git a/test/interface6.go b/test/interface6.go
index 8bfcdf0..c675595 100644
--- a/test/interface6.go
+++ b/test/interface6.go
@@ -6,6 +6,8 @@
 
 package main
 
+import "os"
+
 var fail int
 
 func check(b bool, msg string) {
@@ -145,6 +147,6 @@
   f11();
   f12();
   if fail > 0 {
-    sys.Exit(1)
+    os.Exit(1)
   }
 }