Returns whether the TradeSkill UI is showing another player's skill
See also Tradeskill functions.
Signature:
isLinked, name = IsTradeSkillLinked()
Returns:
isLinked- 1 if the TradeSkill APIs currently reflect another character's tradeskill; nil if showing the player's tradeskill or if no skill is shown (1nil)name- If showing another character's skill, the name of that character (string)