Support the login_hint parameter
Support the login_hint parameter

Add support for setting the login_hint parameter which can simplify the authorization flow if the application knows the email address or domain the user should authenticate with. The parameter is defined at: https://developers.google.com/accounts/docs/OAuth2WebServer#formingtheurl
clancychilds/oauth2client,google/oauth2client,googleapis/oauth2client,google/oauth2client,jonparrott/oauth2client,googleapis/oauth2client,clancychilds/oauth2client,jonparrott/oauth2client