ipproto values are missing on Windows

**Environment Information**
jruby 9.2.10.0-SNAPSHOT (2.5.7) 2020-02-15 fffffff Java HotSpot(TM) 64-Bit Server VM 11.0.1+13-LTS on 11.0.1+13-LTS +jit [mswin32-x86_64]

**Expected Behavior**
```ruby
require 'socket'
Socket::IPPROTO_UDP
=> 17
```

**Actual Behavior**
```ruby
require 'socket'
Socket::IPPROTO_UDP
=> 9
```

fixed by https://github.com/jnr/jnr-constants/pull/65