added rand functions to AbstractRNG

Author: sivasathyaseeelan

src/PoissonRandom.jl

@@ -13,6 +13,10 @@ rand(rng::PassthroughRNG) = Random.rand()
 randexp(rng::PassthroughRNG) = Random.randexp()
 randn(rng::PassthroughRNG) = Random.randn()
 
+rand(rng::AbstractRNG) = Random.rand(rng)
+randexp(rng::AbstractRNG) = Random.randexp(rng)
+randn(rng::AbstractRNG) = Random.randn(rng)
+
 count_rand(λ) = count_rand(Random.GLOBAL_RNG, λ)
 function count_rand(rng::AbstractRNG, λ)
     n = 0