Relax limits of FCurve Bézier handles during evaluation. FCurve handles can be scaled down to avoid the curve looping backward in time. This scaling was done correctly but over-carefully, posing unnecessary limitations on the possible slope of FCurves. This commit changes the scaling approach such that the FCurve can become near-vertical. Bump Blender's subversion from 291.0.1 to 291.0.2 to ensure that older animation files are correctly updated. Reviewed By: sybren Differential Revision: https://developer.blender.org/D8752