FIX: don't bias random feature selection
FIX: random number generator

FIX: address @larsmans + @ogrisel comments

ENH: add INT32_t type

ENH: rename INT32_t to UINT32_t

FIX: modulo RAND_R_MAX+1

FIX: broken tests
FIX: module RAND_R_MAX
TEST: improve test_distribution
TEST: improved test_distribution
FIX: use XorShift random number generator
DOC: remove rand_r license
Merge pull request #2442 from glouppe/tree-shuffle

[MRG] Trees: random features selection is biased