r1039: Fixed titler bug: occasional full intensity flash at last frame
Bug: Titles configured to fade out sometimes flashed the title at full
intensity at the last frame of the effect range.
The problem was a boundary condition of the alpha calculation such that if
the last frame of the effect was exactly aligned with a frame boundary,
alpha would be set to 1 instead of 0.
Also changed some integer truncation to rounding, although this wasn't
related to the bug.
[j6t: use lroundf(...) instead of (int)roundf(...)]
Patch by Craig Lawson.