Ruby » Ruby master

merge revision(s) 37296: [Backport #7205]

    * configure.in (visibility_option): visibility attribute is not
      available before GCC 4, so do not use -fvisibility option in that
      case.  [ruby-core:48147] [Bug #7205]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@37552 b2dd03c8-39d4-4d8f-98ff-823fe69b080e