console.c: dead code

* ext/io/console/console.c: remove dead code for old versions.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48877 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io-console.gemspec: bump up

* ext/io/console/io-console.gemspec: bump up to 0.4.3.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48878 b2dd03c8-39d4-4d8f-98ff-823fe69b080e