Merge branch 'jk/http-auth-keyring' into next

Merge branch 'jk/http-auth-keyring' into next

* jk/http-auth-keyring:
  credentials: add "getpass" helper
  credentials: add "store" helper
  credentials: add "cache" helper
  docs: end-user documentation for the credential subsystem
  http: use hostname in credential description
  allow the user to configure credential helpers
  look for credentials in config before prompting
  http: use credential API to get passwords
  introduce credentials API
  http: retry authentication failures for all http requests
  remote-curl: don't retry auth failures with dumb protocol
  improve httpd auth tests
  url: decode buffers that are not NUL-terminated

Conflicts:
	Documentation/Makefile