io/wait is expected to work on any platform where sockets are
supported. io/wait methods uses fewer allocations and uses
ppoll internally under Linux for better performance on
high-numbered FDs.
[ruby-core:35572] describes the performance advantage of ppoll
on high-numbered FDs.
* lib/net/protocol.rb (rbuf_fill): use IO#wait_*able
* lib/net/http/generic_request.rb (wait_for_continue): ditto
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50326 b2dd03c8-39d4-4d8f-98ff-823fe69b080e