fix SumW2Error correction

two oversights are now fixed:
1. TMatrixDSym is not really symmetric, i.e. changing M(i, j) does not
   change M(j, i), so add a for loop which does that after inversion
   (since the inversion routine only fills the diagonal and below)
2. the new matrix inversion with Cholesky decomposition was not used for
   the old minimiser

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
implement analytical integrals of RooHistPdf over subranges

RooHistPdf provides analytical integrals, but the result ignores the
range parameter completely. This patch updates RooHistPdf and the
underlying RooDataHist class to provide this functionality.

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
fix initialisation hazard in RooDataHist

previous patch to RooDataHist could leave the new _binbounds array
uninitialised before it was used, so we check explicitly

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
RooAbsReal: recognize RooFit::Minimizer in chi2FitTo, pass on full RooFit::Optimize setting

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
sanitise RooAbsArg leafNodeServerList, branchNodeServerList and treeNodeServerList

joining the sets returned by the former two methods should form the set
returned by the latter

otherwise, this implies that we have nodes in the expression tree which
are neither leaf nor branch nodes

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>
BidirMMapPipe.h: fix for very old versions of Mac OS/X

Signed-off-by: Wouter Verkerke <verkerke@nikhef.nl>