(By Lawrence Toppman, ltoppman@charlotteobserver.com) The national tour of "Mamma Mia" reaches Charlotte about as often as elections for the U.S. House of Representatives. So the lone question playgoers are likely to have is this: Does this fifth version differ significantly from the ones that have bounced through Belk Theater every couple of seasons since 2002?I can't relate it to any but the last, which I enjoyed just as much.