Track the selected xtrn-section lightbar position

Fixes the scrolled/selected position when the sysop has more than screen-full of xtrn program sections. As reported by mlong.

src/sbbs3/scfg/scfgxtrn.c

@@ -2242,7 +2242,7 @@ int natvpgm_cfg()
 
 void xtrnsec_cfg()
 {
-	static int xtrnsec_dflt,xtrnsec_opt;
+	static int xtrnsec_dflt,xtrnsec_bar,xtrnsec_opt;
 	char str[128],code[128],done=0;
 	int j,k;
 	uint i;
@@ -2271,7 +2271,7 @@ void xtrnsec_cfg()
 			"\n"
 			"To configure an online program section, select it and hit ~ ENTER ~.\n"
 		;
-		i=uifc.list(j,0,0,45,&xtrnsec_dflt,0,"Online Program Sections",opt);
+		i=uifc.list(j,0,0,45,&xtrnsec_dflt,&xtrnsec_bar,"Online Program Sections",opt);
 		if((signed)i==-1)
 			return;
 		int msk = i & MSK_ON;