more pictureflow work:

more pictureflow work:

remove create_bmp entirely, storing scaled covers as-is in cache

extend accuracy of fade_color and use it for reflection fading

fix rendering issues while working on renderer, it is slower now but
outside edge of cover no longer cuts off top of next cover if it would
be exposed

fix fsin to have real -1.0 - 1.0 range, and have correct zeroes

adjust center margin option range again, now 0-80, since negative
causes rendering glitches

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19603 a1c6a512-1295-4272-9138-f99709370657