it builds again.

Finished revising the inode structure and loading such that:
	if loaded from disk.
	ci->on_disk == 1
		meaning the inode either was loaded from disk
		or has been assigned an entry there
	ci->dsk_ientry_loc
		points to where the ientry is found in the parent
		inode's itbl, chunk and entry offset

	cfs_inode_init -- only to be called for inodes loaded from
			disk. change this later to reflect that.

	ci->parent now points to parent inode, always, it will
	__iget the ref on initialisation and iput it on drop_inode,
	which does just that before handing off to generic_drop_inode

	NEXT STEP:
	revise layout slightly, ensure first entry is butchered and
	repurposed to be a free-list and a sorted list of 1b offsets
	into the chunk.
	Change lookup code to work with this

	=> stationary ientry positions
		=> less writing on re-sort
		=> fixed entries for skipping lookups in writing
			dirty changes, just *WRITE*

Signed-off-by: Jesper Madsen <jmad@itu.dk>
Added backing device info struct determining what the page cache can be used for.
With it, I also added a read-ahead value of 128kb

Other minor bugfixes, fs can now be created, mounted and unmounted again. In preparation for the chunk
format change.
FS creation works again, so does mounting & unmounting.
There's bound to be errors, however. A few errors were found and corrected in the process of refactoring,
chiefly to move chunk-related code out to its own module, chunk.{c,h}.
"Finished" refactoring chunk code, wrote chunk and itbl functions for reading, writing chunks easily,
updating an ientry in a chunk, deleting an ientry from a chunk, inserting an ientry into a chunk. Grabbed
and refactored linux/sort.h implementation enough to work with my idea of using the off_list for sorting and
having the comparator build the addresses to the actual entries by getting a third parameter, the address to
the base of the entries array.

So far so good, next up is tying in the super functions (FINALLY) to manage the lifecycle of an inode.