* lib/matrix.rb: add Matrix#antisymmetric?. Proposed by Yilo (@yiloo). Patch by Marcus Stollsteimer (@stomar). [Fix GH-1788] * spec/ruby/library/matrix/antisymmetric_spec.rb: add specs. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61775 b2dd03c8-39d4-4d8f-98ff-823fe69b080e