stata2libsvm() works now
stata2libsvm() works now

Figuring out that the end-of-row was signalled by a -1 was tricky.
There's no comment about that in libsvm's svm.h nor even in svm-train.c

This also adds svm_problem_pprint() for debugging, and I've pasted it into
svm-train.c and gotten identical output, whic his how I am so confident.

quevedin/statasvm,quevedin/statasvm,quevedin/statasvm