Working on the logging API exposed to scripts.

- Moving all functions into the Log::* namespace, using the recent
  bifcl updates. Moved logging-specific stuff to logging.bif.

- Log::create_stream() now takes a record Log::Stream as its second
  argument, which specifies columns and (optionally) the event.

- All the internal BiFs are now called "Log::__<something>", with
  script-level wrappers "Log::<something>". That first allows to add
  additional code at the script-level, and second makes things better
  comprehendible as now all relevant functionality is collected (and
  later documetned) in policy/logging.bro.

- New function Log::flush(id), which does the obvious assuming the
  writer supports it.

- add_default_filter() is now called implicitly with every
  create_stream(). Seems that we usually want that functionality, and
  when not, remove_default_filter() gets rid of it.

- The namespace of a stream's ID is now used as the default "path"
  (e.g., if the namespace is SSH, the default log file is "ssh.log").

- Updated policy/test-logging.bro as well as the btest tests according
  to these changes.

src/NetVar.cc

@@ -260,11 +260,10 @@ int record_all_packets;
 RecordType* script_id;
 TableType* id_table;
 
-RecordType* log_filter;
-
 #include "const.bif.netvar_def"
 #include "types.bif.netvar_def"
 #include "event.bif.netvar_def"
+#include "logging.bif.netvar_def"
 
 void init_event_handlers()
 	{
@@ -320,6 +319,7 @@ void init_net_var()
 	{
 #include "const.bif.netvar_init"
 #include "types.bif.netvar_init"
+#include "logging.bif.netvar_init"
 
 	conn_id = internal_type("conn_id")->AsRecordType();
 	endpoint = internal_type("endpoint")->AsRecordType();
@@ -568,6 +568,4 @@ void init_net_var()
 
 	script_id = internal_type("script_id")->AsRecordType();
 	id_table = internal_type("id_table")->AsTableType();
-
-	log_filter = internal_type("log_filter")->AsRecordType();
 	}