adjustment: Fix elasticity
adjustment: Fix elasticity

Fix the 'elastic' mode so that it works as it's described in the property
description. That is to say, it disables clamping and when interpolating
outside of the lower/upper-page_size range, it will bounce back to the
edge of the boundary.

pwithnall/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx