Agence France-Presse: High winds and rough seas hampered efforts Saturday to prevent a giant oil slick from reaching US shores and wreaking enormous environmental and economic damage on the fragile Louisiana coast. President Barack Obama prepared for a Sunday morning visit to the stricken region in the Gulf of Mexico, a prime spawning ground for fish, shrimp and crabs, home to oyster beds and a major stop for migratory birds. The leading edge of the slick may just be sheen, but Louisiana governor …