Added stealth checking support

[FeikoWielsma]

I tested it on my druid; worked fine for me. First time editing Lua, though!

[DanielAdolfsson]

Great! But I'm not sure 16 is the maximum number of buffs. I suspect UnitBuff returns nil if a buff doesn't exist on that index.

[DanielAdolfsson]

local i, buff = 1
repeat
    buff = UnitBuff("player", i);
    if buff == textureName then
        return true
    end
    i = i + 1
until not buff
return false