FIX call srand whenever random_seed >= 0 in libsvm

This bug was discovered by #3691 (failing test under windows).
Merge pull request #3730 from ogrisel/fix-libsvm-random-seed

[MRG+1] FIX call srand whenever random_seed >= 0 in libsvm
MAINT missing numpy / scipy for the Python 3.3 build

Building scikit-learn on Python 3.3 on appveyor would first require
building numpy and scipy wheels.

Disabling in the mean time.
Merge remote-tracking branch 'upstream/master'