Update math/R-cran-car to 2.0-21.

ChangeLog:

• residualPlot error when using 'type="rstudent" has been fixed.
• Minor change to "recode" documentation; improved error checking in recode().
• Fixed a bug in gamLine with non-canonical links. (Thanks to Hani Christoph)
• Added has.intercept.multinom() to make Anova() work with multinom objects fit to a dichotomous response (after bug report by Kristian Hovde Liland).
• Replaced vif.lm() with vif.default() to cover wider variety of models (after question by Laura Rigg about gls models).
• Diagonal panels in scatterplotMatrix() (except for histograms) show groups separately when plotted by groups (suggestion by Erich Neuwirth).
• Added vcov. argument to Anova.lm().