CHARLOTTE, N.C. — Despite nearly 25,000 supporters, a public campaign asking McDonald’s and Starbucks to install anti-pornography filters on their in-store free Wi-Fi networks has so far been unsuccessful. The “Porn Free Wi-Fi” campaign, organized by the Internet safety group Enough is Enough (EIE), is urging the fast-food and coffee giants to implement Internet filters in their U.S. stores to…