Incremental commit: add fat CLI tool

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Incremental commit

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
fat: Catch and print block device errors

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Incremental commit
Regenerate OASIS

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Use the Io_page allocator rather than the one from mirage-block
Try to make the error handling binds a bit more explicit
Merge pull request #9 from djs55/fat

Functorise over memory allocator