This change runs into a bug in visual studio 2005 that I can't seem
to find a way to avoid.  Might try it again later, but for now, I'm backing
it out.

in the data.

--HG--
rename : dlib/svm/structural_svm_potts_problem.h => dlib/svm/structural_svm_graph_labeling_problem.h
rename : dlib/svm/structural_svm_potts_problem_abstract.h => dlib/svm/structural_svm_graph_labeling_problem_abstract.h

elements should be non-negative rather than just being able to say
all or none of them are non-negative.

undirected graph rather than the special purpose potts_problem type
object.

just an approximate answer.