not included in root-config --libs

Hi root developers,

I am using THistPainter::ProjectAitoff2xy() directly to generate sky maps. During compilation I was getting “undefined reference to” error messages because is not listed in root-config --libs(actually I am using the autotools macros) so I have to include -lHistPainter manually in my Makefile. I suppose not many users will have this problem since THistPainter is normaly indirectly used via the histograms classes, but it may be usefull to list it in the --libs flag.

Best regards

or may be THistPainter::ProjectAitoff2xy() should be move in some more general library like Math …