lrsnash isn't thread-safe

[btwied]

Running the following program with -t 1 and -t 8 gives very different results!

using Base.Threads: @threads
using GameTheory: NormalFormGame, lrsnash

@threads for i in 1:200
    if length(lrsnash(NormalFormGame(rand(0:999, 2,2,2)))) == 0
        println("No equilibria found!")
    end
end