b2Shape_SetFriction() doesn't update friction of existing contacts

[notnullnotvoid]

I believe the same is also true of b2Shape_SetRestitution(), and maybe the various functions that update body mass data, but I'm not totally sure. It seems the computed values for these properties in b2ContactSim don't get updated as long as the two shapes remain in contact. Admittedly, this is probably a fairly niche use case, but it is one I ran into. I'm currently working around this by disabling and re-enabling the body to force contacts to get re-created, which works well enough for my use case where I'm changing these properties infrequently, but it would be ideal to have a more lightweight way to ensure the contacts' properties get updated.

[erincatto]

These are now updated in the narrow phase. #873