[Rd] qpois errors for degenerate distribution (PR#14135)

[Jerry.Lewis at biogenidec.com]

Full_Name: Jerry W. Lewis
Version: 2.10.0
OS: XP Professional
Submission from: (NULL) (96.237.55.233)


For a degenerate Poisson distribution (lambda==0), qpois(p,0,lower.tail) should
return 0 for any valid p, but qpois(1,0) and qpois(0,0,F) incorrectly return
Inf.