using &*_expire with interval values defined before

policy-script:
> const tcp_scan_period = 2 min &redef;
> global tcp_scan: table[addr] of count &write_expire=tcp_scan_period;

error:
> line xx (tcp_scan_period): bad tag in ExprVal::Val

Here's a patch to fix the bug. (Also, a work-around would be to instead
stick "2 min" directly in rather than using a variable.) This will be
included in the upcoming release.

    Vern

--- Val.cc.ORIG 2005/02/07 23:46:08 1.1
+++ Val.cc 2005/02/08 00:49:59
@@ -1490,7 +1490,7 @@

   if ( a )
     {
- expire_time = a->AttrExpr()->ExprVal()->AsInterval();
+ expire_time = a->AttrExpr()->Eval(0)->AsInterval();

     // As network_time is not necessarily initialized yet,
     // we set a timer which fires immediately.