[Rd] heatmap documentation typo

[Martin Maechler]

>>>>> Jonathan Dushoff <dushoff at mcmaster.ca>
>>>>>     on Thu, 30 Jun 2011 14:09:30 -0400 writes:

    > Under Details, the documentation says "[if Rowv or Colv] is 'NULL',
    > _no reordering_ will be done for the corresponding side."  In fact, as
    > explained elsewhere in the documentation, 'NA' is required, not
    > 'NULL'.

    > An anonymous expert suggested that I should attach an svn diff file to
    > this report, so I will.

Not necessary.  I've now committed the fix.

Thank you, Jonathan, for the report.

Martin Maechler, ETH Zurich

    > ----------------------------------------------------------------------
    > Index: heatmap.Rd
    > ===================================================================
    > --- heatmap.Rd	(revision 56237)
    > +++ heatmap.Rd	(working copy)
    > @@ -94,7 +94,7 @@
    > If either is missing, as by default, then the ordering of the
    > corresponding dendrogram is by the mean value of the rows/columns,
    > i.e., in the case of rows, \code{Rowv <- rowMeans(x, na.rm=na.rm)}.
    > -  If either is \code{\link{NULL}}, \emph{no reordering} will be done for
    > +  If either is \code{\link{NA}}, \emph{no reordering} will be done for
    > the corresponding side.
 
    > By default (\code{scale = "row"}) the rows are scaled to have mean

    > ----------------------------------------------------------------------