AppVeyor CI (Windows) builds failing with net-ssh 4.0.0

[mattbrictson]

Windows builds are failing with errors like this:

bundle exec rake
C:/Ruby21/lib/ruby/2.1.0/fiddle/cparser.rb:90:in `parse_signature': can't parse the function prototype: HANDLE CreateFileMapping(HANDLE, void *, DWORD, ' + 'DWORD, DWORD, LPCTSTR) (RuntimeError)
	from C:/Ruby21/lib/ruby/2.1.0/fiddle/import.rb:162:in `extern'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:101:in `<module:Win>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:41:in `<module:Pageant>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:33:in `<module:Authentication>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:24:in `<module:SSH>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:24:in `<module:Net>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/pageant.rb:24:in `<top (required)>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/agent.rb:9:in `require'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/agent.rb:9:in `<top (required)>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/key_manager.rb:4:in `require'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/key_manager.rb:4:in `<top (required)>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/session.rb:4:in `require'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh/authentication/session.rb:4:in `<top (required)>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh.rb:12:in `require'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/net-ssh-4.0.0/lib/net/ssh.rb:12:in `<top (required)>'
	from C:/Ruby21/lib/ruby/gems/2.1.0/gems/sshkit-1.11.5/lib/sshkit/backends/netssh.rb:4:in `require'

See: https://ci.appveyor.com/project/mattbrictson/airbrussh/build/154/job/aejc0ds8mi1o6qlb