Function: sumalt
Section: sums
C-Name: sumalt0
Prototype: V=GED0,L,p
Help: sumalt(X=a,expr,{flag=0}): Cohen-Villegas-Zagier's acceleration of
 alternating series expr, X starting at a. flag is optional, and can be 0:
 default, or 1: uses a slightly different method using Zagier's polynomials

