Add a field mount_cookie to the partition_data structure and

respective setter/getter methods to the KPartition class.
If a partition is mounted, the field will contain the cookie the
FS's mount() hook passed back to the VFS. This way the FS has
access to its internal data structures. We need the cooperation
of the VFS to get the cookie.


git-svn-id: file:///srv/svn/repos/haiku/trunk/current@4776 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/disk_device_manager/disk_device_manager.h

@@ -28,6 +28,7 @@ typedef struct partition_data {
 	uint32			status;			// [sys]
 	uint32			flags;
 	dev_t			volume;			// [sys]
+	void			*mount_cookie;	// [sys] 
 	char			*name;			// max: B_OS_NAME_LENGTH
 	char			*content_name;	//
 	char			*type;			//