outGain is always zero in this branch.

Imagine a font with current min/default/max of 100,700,1000. And new
setting of 100,400,1000. The current normalizeLocation will calculate
the new location for 700 to be +.33, whereas it should calculate +.5!
This is because 400 translates to -.5, so 700 will be normalized to
-1,-.5,+1 and get +.33...

We need a special normalizeLocation that is aware of the "distance"
between min/default/max, ie. the non-normalized values. Then it will be
clear that the distance from 400 to 700 is equal to 700 to 1000, and as
such 700 should be normalized to .5, not .33... I'm still trying to
figure out the case where avar is present.

Store this distance in NormalizeAxisLimit and reach it out in the
solver.

Fixes #3177