Extending the log writer DoInit() API.

We now pass in a Info struct that contains:

    - the path name (as before)
    - the rotation interval
    - the log_rotate_base_time in seconds
    - a table of key/value pairs with further configuration options.

To fill the table, log filters have a new field "config: table[string]
of strings". This gives a way to pass arbitrary values from
script-land to writers. Interpretation is left up to the writer.

Also splits calc_next_rotate() into two functions, one of which is
thread-safe and can be used with the log_rotate_base_time value from
DoInit().

Includes also updates to the None writer:

    - It gets its own script writers/none.bro.

    - New bool option LogNone::debug to enable debug output. It then
      prints out all the values passed to DoInit(). That's used by a
      btest test to ensure the new DoInit() values are right.

    - Fixed a bug that prevented Bro from terminating..

(scripts.base.frameworks.logging.rotate-custom currently fails.
Haven't yet investigated why.)

src/Val.cc

@@ -1651,6 +1651,7 @@ int TableVal::RemoveFrom(Val* val) const
 	while ( (v = tbl->NextEntry(k, c)) )
 		{
 		Val* index = RecoverIndex(k);
+
 		Unref(index);
 		Unref(t->Delete(k));
 		delete k;