Rename displaySave member of the stack frame to padding. (r=luke)

js/src/jsinterp.h

@@ -141,13 +141,13 @@ struct JSStackFrame
     JSObject        *blockChain;
 
     uint32          flags;          /* frame flags -- see below */
-    JSStackFrame    *displaySave;   /* previous value of display entry for
-                                       script->staticLevel */
 
     /* Members only needed for inline calls. */
     void            *hookData;      /* debugger call hook data */
     JSVersion       callerVersion;  /* dynamic version of calling script */
 
+    void            *padding;
+
     void putActivationObjects(JSContext *cx) {
         /*
          * The order of calls here is important as js_PutCallObject needs to