re-export MessageConnection so that vscode-languageserver/client is self contained (#598)
re-export MessageConnection so that vscode-languageserver/client is self contained (#598)

MessageConnection is exposed through CanellationSenderStrategy
microsoft/vscode-languageserver-node,microsoft/vscode-languageserver-node,microsoft/vscode-languageserver-node,microsoft/vscode-languageserver-node