added LLProgressView::abortShowProgress. Issue upon failed login to terminate pending loginpanel destruction which was killing the actual 'new' replacement loginpanel instead of the old to-be-deleted version.

indra/newview/llviewerwindow.h

@@ -280,6 +280,7 @@ public:
 	void			setProgressCancelButtonVisible( BOOL b, const std::string& label = LLStringUtil::null );
 	LLProgressView *getProgressView() const;
 	void			revealIntroPanel();
+	void			abortShowProgress();
 	void			setStartupComplete();
 
 	void			updateObjectUnderCursor();