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/Func.cc

@@ -508,6 +508,7 @@ void builtin_run_time(const char* msg, BroObj* arg)
 	}
 
 #include "bro.bif.func_h"
+#include "logging.bif.func_h"
 
 #include "common-rw.bif.func_h"
 #include "finger-rw.bif.func_h"
@@ -519,6 +520,7 @@ void builtin_run_time(const char* msg, BroObj* arg)
 #include "dns-rw.bif.func_h"
 
 #include "bro.bif.func_def"
+#include "logging.bif.func_def"
 #include "strings.bif.func_def"
 
 void init_builtin_funcs()
@@ -530,6 +532,7 @@ void init_builtin_funcs()
 	gap_info = internal_type("gap_info")->AsRecordType();
 
 #include "bro.bif.func_init"
+#include "logging.bif.func_init"
 
 #include "common-rw.bif.func_init"
 #include "finger-rw.bif.func_init"