Several modifications to smart_scrolling.py

- file smart_scrolling.py renamed to scrolling.py
- class SmartScrolling renamed to Scrolling
- method scroll renamed to scroll_smartly
- _bresenham_sums is now a static method
- simple cache for Bresenham sums
- new method scroll_to_predefined
- smart scrolling ensures increment by at least 1 px
- max_scroll is not a field anymore
- minor refactoring



git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@926 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Enable double buffering for all platforms.

This might not be perfect, but it's way better than before.


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@927 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Simpler interface for Scrolling.scroll_smartly


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@928 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Bug fix.


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@929 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Revert "Fix "Fit to Width" not scaling up small images."

This reverts commit 747b9b2484fd831b48154056439ddabf6b4c65c3.
My bad, the previous behaviour was just fine.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@930 ef8490bc-f317-4725-81ed-e95a9aca1bcf