Make xroute_gc_delay a named constant.

babel.c

@@ -741,7 +741,7 @@ expire_routes(void)
     i = 0;
     while(i < numxroutes) {
         struct xroute *xroute = &xroutes[i];
-        if(xroute->time < now.tv_sec - 240) {
+        if(xroute->time < now.tv_sec - xroute_gc_delay) {
             flush_xroute(xroute);
             continue;
         }

xroute.c

@@ -39,6 +39,8 @@ int numxroutes = 0;
 struct xroute myxroutes[MAXMYXROUTES];
 int nummyxroutes = 0;
 
+int xroute_gc_delay = 180;
+
 static struct xroute *
 find_installed_xroute(unsigned char *prefix, unsigned short plen)
 {

xroute.h

@@ -38,6 +38,8 @@ extern int numxroutes;
 extern struct xroute myxroutes[MAXMYXROUTES];
 extern int nummyxroutes;
 
+extern int xroute_gc_delay;
+
 void install_xroute(struct xroute *xroute);
 void uninstall_xroute(struct xroute *xroute);
 void consider_xroute(struct xroute *xroute);