The Charlie Hebdo murders focused attention on the threat to Western satirists, but political cartoonists around the world are at risk. Some, such as cartoonists from Iran and China, live in exile so they can continue with their political commentary. Their status brings fresh urgency to longstanding questions around the limits of free speech, the role of satire as a form of dissent, and the relationship between political cartooning and journalism.   Above Photo: Francois Mori/Associated Press Cover Illustration: Christopher Weyant