Require that users have a non-deprecated database module loaded.

modules/database/db_flatfile.cpp

@@ -80,6 +80,8 @@ public:
 	DBFlatFile(const Anope::string &modname, const Anope::string &creator)
 		: Module(modname, creator, DATABASE | DEPRECATED | VENDOR)
 	{
+		if (!ModuleManager::FindFirstOf(DATABASE, this))
+			throw ModuleException("db_flatfile is deprecated and can only import old databases.");
 	}
 
 	EventReturn OnLoadDatabase() override