LONDON, June 19 — Advances in cellphone technology have spurred an insidious new threat — the use of the increasingly popular camera phones by pedophiles to photograph children. Across Britain, swimming pools and sports facilities have cracked down on their use while the YMCA in the Australian state of Victoria has also imposed a ban. Officials have yet to raise a clamor in the United States, where the devices have only recently become widely available. U.K. PARENTS AND child protection agencies say they worry that pedophiles will use the state-of-the-art camera phones to surreptitiously photograph children in changing rooms, instantly...