#2226 itensor redefines sdiff / problem with binomial

[Barton Willis]

OK:

(%i1) diff(binomial(k,n),k);
(%o1) -binomial(k,n)*(psi[0](-n+k+1)-psi[0](k+1))

(%i2) load(itensor)$

Not OK

(%i3) diff(binomial(k,n),k);
(%o3) 'diff(binomial(k,n),k,1)