Instance: add Database attribute

Move from db/DatabaseGlue.cxx, eliminating global variable.

src/client/Client.cxx

@@ -20,5 +20,17 @@
 #include "config.h"
 #include "ClientInternal.hxx"
 #include "util/Domain.hxx"
+#include "Partition.hxx"
+#include "Instance.hxx"
 
 const Domain client_domain("client");
+
+#ifdef ENABLE_DATABASE
+
+const Database *
+Client::GetDatabase(Error &error) const
+{
+	return partition.instance.GetDatabase(error);
+}
+
+#endif

src/client/Client.hxx

@@ -38,6 +38,7 @@ struct sockaddr;
 class EventLoop;
 class Path;
 struct Partition;
+class Database;
 
 class Client final : private FullyBufferedSocket, TimeoutMonitor {
 public:
@@ -169,6 +170,11 @@ public:
 	 */
 	bool AllowFile(Path path_fs, Error &error) const;
 
+	/**
+	 * Wrapper for Instance::GetDatabase().
+	 */
+	const Database *GetDatabase(Error &error) const;
+
 private:
 	/* virtual methods from class BufferedSocket */
 	virtual InputResult OnSocketInput(void *data, size_t length) override;