Blender Git Loki

Fix T39207: FCurve evaluation regressions following 2aff243 (again)

Yet another attempt at fixing the problems here. This time, I've added a new
function/version of the binary search utility so that we can pass in custom
thresholds (Note: This ability is only used for evaluation currently, with
everything else using a wrapper which still uses the old default threshold),
making it ok to start trusting the "exact" parameter.