Update math/R-cran-car to 2.0-20.

ChangeLog:
o Added new id.method="r" to showLabels for labeling plots of residuals;

default id.method changed in residualPlots.

o Fixed handling of labels argument to outlierTest()

(bug report by Stephane Laurent).

o Accommodate numeric variables consisting entirely of NAs in recode()

(suggestion of Karl Ove Hufthammer).

o Prevent dataEllipse() from opening a graphics device when draw=FALSE

(fixing bug reported by Rafael Laboissiere).

o The functions makeHypothesis() and printHypothesis(), intended for

internal use, are exported so that they can be used in other packages
(request of Arne Henningsen).

o Small fixes.