A stupid hack is needed here, changing the way the factor is applied to
angular bending springs. In cloth sim the bending factor of individual
springs is applied as a mix value between the bending stiffness and a
max value, but this max value isn't even used in hair sim so that
approach becomes useless.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
60bf6c123f