The common truncf(x + 0.5) fails for the floating-point value just less
than 0.5 (nextafterf(0.5, 0.0)). nextafterf(0.5, 0.0) + 0.5, after
rounding is 1.0, thus truncf does not produce the desired value.
The solution is to add nextafterf(0.5, 0.0) instead of 0.5 before
truncating. This works for all values.
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
2d48d5116b