* U.S, other Western nations say pulling out citizens
* President Kiir calls fighting a coup attempt
* Clashes revive memories of bloody ethnic rifts in 1990s
By Andrew Green
JUBA, Dec 18 (Reuters) - Fighting between South Sudanese soldiers spread to the flashpoint town of Bor on Wednesday, raising fears of a broader civil conflict in the two-year-old nation.
An official in...