math.c: C99-like atan2
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45805 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
math.c: C99-like atan2
both two arguments are infinity. based on the patch by cremno
phobia in [ruby-core:62310]. [Feature #9799]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45805 b2dd03c8-39d4-4d8f-98ff-823fe69b080e