* include/sys/dirent.h (struct __DIR): Rename __d_unused to

	* include/sys/dirent.h (struct __DIR): Rename __d_unused to
	__d_internal.
	* fhandler_disk_file.cc (struct __DIR_cache): Remove useless "typedef".
	(d_dirname): Remove useless "struct".
	(d_cachepos): Ditto.
	(d_cache): Ditto.
	(class __DIR_mounts): New class, implementing mount point tracking
	for readdir.
	(d_mounts): New macro for easy access to __DIR_mounts structure.
	(fhandler_disk_file::opendir): Allocate __DIR_mounts structure and
	let __d_internal element of dir point to it.
	(fhandler_disk_file::readdir_helper): Add mount points in the current
	directory, which don't have a real directory backing them.
	Don't generate an inode number for /dev.  Add comment, why.
	(fhandler_disk_file::readdir): Move filling fname to an earlier point.
	Check if current entry is a mount point and evaluate correct inode
	number for it.
	(fhandler_disk_file::readdir_9x): Ditto.
	(fhandler_disk_file::rewinddir): Set all mount points in this directory
	to "not found" so that they are listed again after calling rewinddir().
	(fhandler_disk_file::closedir): Deallocate __DIR_mounts structure.
	* path.cc (mount_info::get_mounts_here): New method to evaluate a list
	of mount points in a given parent directory.
	* shared_info.h (class mount_info): Declare get_mounts_here.