Don't set 2,5 GB as default minimum required disk

[mariodebian]

Binary package hint: ubiquity

in file: /lib/partman/automatically_partition/10resize_use_free/do_option

There is a line:

maxsize="$(expr "$maxsize" - \( 2 \* 1024 + 510 \) \* 1024 \* 1024)"

That sets 2,5 GB as default minimum size for new Ubuntu partition.

With new filesystem.size file (/cdrom/casper/filesystem.size) we can calculate this.

This bug don't appear to affect the normal Ubuntu CDROM isos, but derivate DVD based on Ubuntu could need at least 8GB.

I propose:

maxsize= maxsize - (filesystem.size + [510 or 1020] )
.
Users can use more than this minimum, but its a failsafe setting.

Our derivative overwrite: http://bit.ly/9s5sdl