Random draw from Poisson fails for large lambda

[jsbryan4]

When using "e" notation for large numbers, I notice that the Poisson distribution fails for orders of magnitude greater than 18.

For example look at the following code and output

using Distributions

println(rand(Poisson(1.0e10)))
println(rand(Poisson(1.0e11)))
println(rand(Poisson(1.0e12)))
println(rand(Poisson(1.0e13)))
println(rand(Poisson(1.0e14)))
println(rand(Poisson(1.0e15)))
println(rand(Poisson(1.0e16)))
println(rand(Poisson(1.0e17)))
println(rand(Poisson(1.0e18)))
println(rand(Poisson(1.0e19)))   # <---- Fails
println(rand(Poisson(1.0e20)))

9999837095
99999767161
1000000268447
10000002717295
100000005394573
1000000029583672
9999999992683622
99999999934764640
1000000000632877824
ERROR: InexactError: trunc(Int64, 1.0e19)
Stacktrace:
 [1] trunc
   @ ./float.jl:805 [inlined]
 [2] floor
   @ ./float.jl:367 [inlined]
 [3] PoissonADSampler
   @ ~/.julia/packages/Distributions/DiPwc/src/samplers/poisson.jl:54 [inlined]
 [4] PoissonADSampler
   @ ~/.julia/packages/Distributions/DiPwc/src/samplers/poisson.jl:49 [inlined]
 [5] sampler
   @ ~/.julia/packages/Distributions/DiPwc/src/univariate/discrete/poisson.jl:143 [inlined]
 [6] rand(rng::Random._GLOBAL_RNG, d::Poisson{Float64})
   @ Distributions ~/.julia/packages/Distributions/DiPwc/src/univariate/discrete/poisson.jl:147
 [7] rand(::Poisson{Float64})
   @ Distributions ~/.julia/packages/Distributions/DiPwc/src/genericrand.jl:22
 [8] top-level scope
   @ ~/Desktop/Projects/StructuredIlluminationInference/examples/scratch.jl:14

[devmotion]

I'll close the issue since it is a duplicate of #821.