- manual zoom stretches small images again, if necessary
- img_size renamed to image_size


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@905 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Change internal representation of _user_zoom to logarithmic scale to prevent round-off errors.


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@906 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Use "round half up" instead of "round towards zero" for more accurate aspect ratio (and slightly larger view) when zooming.


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@907 ef8490bc-f317-4725-81ed-e95a9aca1bcf