[R] Incomplete Gamma Functions and GammaDistribution Doc errata.

[Adrian Custer]

My appologies to everyone. 

Prof. Ripley, please realize that I did not intend to suggest that your
mathematics were wrong. My question about mathematical correctness
refered to my presention of your formula as an equation. I have great
admiration for your work and its influences on my field and, therefore,
start with the presumption that all errors must be my own.

Mr. Maechler, please understand that I had no intent to "insult" anyone.
I wanted to communicate three things:

        1) to point out what I understood to be an error in the
        documentation (which you both point out to be my own
        misunderstanding of the terminology).
        
        2) to ask for confirmation that I was interpreting past emails
        correctly.
        
        3) to argue for an R implementation of an incomplete gamma
        mathematical function.

To the R community, please accept my appologies for a message which you
may have taken to be insulting. I am deeply thankful for your work, for
your code and for this email list.

--adrian