PNG and dimension support added.

[livewire]

Over the past month or so, I managed to add png support to roughdraft.
Using this format, the final compiled product is much smaller than any
of the previous options. I also added basic support for dimensions and
created QCad patch to save directly from QCad into the vector bitmap
format.

For the dimension text, I used the cairo image library. As I have done
most of the initial work to make my software compatible, it is
possible that I will replace my original drawing code with routines
from cairo in the future. This is a cleanup task for myself. For
certain image formats, this would also allow antialiasing.

New stuff is here
http://www.starlo.org/repository/roughdraft.tar.gz
http://www.starlo.org/repository/QCad.patch.tar.gz