#4830 Non-total ordering between constant & scalar and scalar

[David Scherfgen]

Spotted by Claude:

(%i1) declare(a, scalar, c, [constant, scalar])$

(%i2) is(a+c = c+a);
(%o2) false

(%i3) ordergreatp(a, c);
(%o3) false

(%i4) ordergreatp(c, a);
(%o4) false

[Stavros Macrakis]

%o2 looks like a simplus bug.
Shouldn't a+c and c+a both simplify to c+a?

[David Scherfgen]

simplus relies great to decide where the terms have to be placed in the resulting sum. In this case, great doesn't work correctly.