git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61972 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
instead of scattering #ifdef HAVE_NANF here and there define our own nan() unless defined elsewhere. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61971 b2dd03c8-39d4-4d8f-98ff-823fe69b080e