IFS: Style fixes
IFSSaver: NULL check style fix
IFSSaver: cast to bigtime_t, not uint64
IFSSaver: Use single-precision floating point math
IFSSaver: Add some better error checking
IFSSaver: style fixes
IFSSaver: style fix, check if NULL explicitly
IFSSaver: remove fBounds variable
IFSSaver: reverse these for consistency.
IFS: Style fixes
IFSSaver: Don't DirectDraw for preview.

The ScreenSaver window is now a BDirectWindow, but, _DrawFractals() makes
the assumption that a direct window means that the screen saver is running full
screen, so, we need to make sure we draw the preview using the
DrawBitmapAsync() method.

Fixes #10832