Fixed a compile error on systems not using g++ corresponding to the addition ot the class TGraphMultiErrors.
Fixed a compile error on systems not using g++ corresponding to the addition ot the class TGraphMultiErrors.

olifre/root,root-mirror/root,root-mirror/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root,karies/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root