By introducing the new 'File_system_registry', we can remove the
knowledge about the actual file-system implementations from the
'Dir_file_system'. Thereby the code becomes more generic, which is
a precondition for using it as the basis for Genode's VFS library.
Issue #999
Access to a block session is provided by using the block file system.
By specifying the label, each block session request can be routed to
the proper block session provider:
! <fstab>
! ...
! <dir name="dev">
! <block name="blkdev0" label="block_session_0" />
! </dir>
! ...
! </fstab>
In addition to this file system, support for the DIOCGMEDIASIZE ioctl
request was added. This request is used by FreeBSD and therefore our
libc to query the size of the block device in bytes.
Fixes#1010.
