Another sign/clearsign related bug?



Hi,
could this bug be related to the sign/clearsign issue discussed 
recently? (bug #2627, 
http://www.math.utexas.edu/pipermail/maxima/2013/033768.html)

Maxima 5.30

(%i4) ode2 ('diff(y,x,2)-k^2*y,y,x);
Is k zero or nonzero?
nonzero;
(%o4) y = %k2 x + %k1

(Wrong; it was assumed that k=0)

It has already been fixed in 5.31 (I don't know how):

Maxima 5.31

(%i4) ode2 ('diff(y,x,2)-k^2*y,y,x);
Is k zero or nonzero?
nonzero;
(%o4) y = %k1*%e^(k*x)+%k2*%e^-(k*x)$

(Correct)

and I was wondering what changed that made ode2 work correctly again and 
whether something similar could be done to solve #2627.

Regards,
Jaime