[Rd] qpois documentation (PR#13743)

[Jerry.Lewis at biogenidec.com]

Full_Name: Jerry W. Lewis
Version: 2.9.0
OS: Windows XP Professional
Submission from: (NULL) (166.186.168.103)


Quantiles for discrete distributions are consitently implemented, but
inconsitently documented.  Help for qpois incorrectly states in the Details
section that
  "The quantile is left continuous: qgeom(q, prob) is the largest integer x such
that P(X <= x) < q."
which disagrees with the implementation; it should read
  "The quantile is defined as the smallest value x such that F(x) >= p, where F
is the distribution function."
Also, this definition should be added to Help for qhyper.