This patch introduces the same presets that are used for proportional editing in the sculpt brush falloff menu. The user can select any of these presets or use the regular custom falloff curve. The presets are hardcoded formulas, so the falloff curve is not used when they are active.
This change improves the general feeling of the brushes and it is more convenient and simpler to use. The CUSTOM curve option should now be used in the case that an unusual deformation is needed, in other cases, the hardcoded curve presets should be the default.
The smooth curve presets is a must in the grab brush, as it fixes the deformation issue with the current custom curve setting. The user may try to adjust the deformation by tweaking the curve, but it is nearly impossible to replicate this desired behavior.
Other brushes that are included in the sculpt branch also rely on this as they need specific hardcoded falloffs to produce the desired effect.