archive/File: eliminate Close(), make destructor virtual instead

src/archive/ArchiveFile.hxx

@@ -22,19 +22,12 @@
 
 class Mutex;
 class Cond;
-struct ArchivePlugin;
 class ArchiveVisitor;
 class InputStream;
 
 class ArchiveFile {
-protected:
-	/**
-	 * Use Close() instead of delete.
-	 */
-	~ArchiveFile() {}
-
 public:
-	virtual void Close() = 0;
+	virtual ~ArchiveFile() noexcept = default;
 
 	/**
 	 * Visit all entries inside this archive.

src/archive/plugins/Bzip2ArchivePlugin.cxx

@@ -49,10 +49,6 @@ public:
 			name.erase(len - 4);
 	}
 
-	virtual void Close() override {
-		delete this;
-	}
-
 	virtual void Visit(ArchiveVisitor &visitor) override {
 		visitor.VisitArchiveEntry(name.c_str());
 	}

src/archive/plugins/Iso9660ArchivePlugin.cxx

@@ -72,10 +72,6 @@ public:
 	void Visit(char *path, size_t length, size_t capacity,
 		   ArchiveVisitor &visitor);
 
-	virtual void Close() override {
-		delete this;
-	}
-
 	virtual void Visit(ArchiveVisitor &visitor) override;
 
 	InputStream *OpenStream(const char *path,

src/archive/plugins/ZzipArchivePlugin.cxx

@@ -57,10 +57,6 @@ public:
 	ZzipArchiveFile(std::shared_ptr<ZzipDir> &&_dir)
 		:dir(std::move(_dir)) {}
 
-	virtual void Close() override {
-		delete this;
-	}
-
 	virtual void Visit(ArchiveVisitor &visitor) override;
 
 	InputStream *OpenStream(const char *path,