Jamie Lynn Spears has given birth, a source tells Usmagazine.com. Daughter Maddie was born Thursday at Mississippi Southwest Regional Medical Center in McComb, Mississippi. Maddie weighed 7 lbs., 11 ounces. This is the first child for 17-year-old actress and her 19-year-old fiance Casey Aldridge, a pipe layer. (Check out pics of Jamie Lynn's baby bump.) On Wednesday, sister Britney and...