message: Add asVersionedTextDocumentIdentifier to the Converter interface
  It can be useful for users of vscode-languageclient.
diff: @@ -18,6 +18,8 @@ export interface Converter {
  asTextDocumentIdentifier(textDocument: code.TextDocument): proto.TextDocumentIdentifier;
  + asVersionedTextDocumentIdentifier(textDocument: code.TextDocument): proto.VersionedTextDocumentIdentifier;
  +
  asOpenTextDocumentParams(textDocument: code.TextDocument): proto.DidOpenTextDocumentParams;
  asChangeTextDocumentParams(textDocument: code.TextDocument): proto.DidChangeTextDocumentParams;
  @@ -432,6 +434,7 @@ export function createConverter(uriConverter?: URIConverter): Converter {
  return {
  asUri,
  asTextDocumentIdentifier,
  + asVersionedTextDocumentIdentifier,
  asOpenTextDocumentParams,
  asChangeTextDocumentParams,
  asCloseTextDocumentParams,
  