Allow CreateHistogram to be called without setting evaluation points
or first calling EvalAsync() and EvalFinished().
Merge remote-tracking branch 'origin/master' into gpu-pdfs
Do not need to set PDF value buffer to use CreateHistogram.  Remove from test.
Unit tests verifying the correct behavior of pdfz for 2D PDFs.
Merge branch 'master' of github.com:mastbaum/sxmc into gpu-pdfs
pdfz integration complete, bar some issues with systematics