new global_options() BiF to speed up startup, plus a micro-preen

scripts/base/frameworks/config/main.zeek

@@ -162,13 +162,7 @@ event zeek_init() &priority=10
 @if ( !Cluster::is_enabled() || Cluster::local_node_type() == Cluster::MANAGER )
 	# Iterate over all existing options and add ourselves as change handlers
 	# with a low priority so that we can log the changes.
-	local gids = global_ids();
-	for ( i, gid in gids )
-		{
-		if ( ! gid$option_value )
-			next;
-
-		Option::set_change_handler(i, config_option_changed, -100);
-		}
+	for ( opt in global_options() )
+		Option::set_change_handler(opt, config_option_changed, -100);
 @endif
 	}

scripts/base/utils/site.zeek

@@ -243,5 +243,4 @@ event zeek_init() &priority=10
 	# Create the local_nets mapping table.
 	for ( cidr in Site::local_nets )
 		local_nets_table[cidr] = cidr;
-
 	}

src/zeek.bif

@@ -2022,6 +2022,25 @@ function global_ids%(%): id_table
 	return ids;
 	%}
 
+## Returns a set giving the names of all global options.
+function global_options%(%): string_set
+	%{
+	auto options = make_intrusive<zeek::TableVal>(zeek::id::string_set);
+	const auto& globals = zeek::detail::global_scope()->Vars();
+
+	for ( const auto& global : globals )
+		{
+		const auto& id = global.second;
+		if ( ! id->IsOption() )
+			continue;
+
+		auto id_name = zeek::make_intrusive<zeek::StringVal>(id->Name());
+		options->Assign(std::move(id_name), nullptr);
+		}
+
+	return options;
+	%}
+
 ## Returns the value of a global identifier.
 ##
 ## id: The global identifier.