* helm-mode.el (helm--completion-in-region): Fix prompt for completion-at-point family that have no prompt.
* helm-mode.el (helm-mode-handle-completion-in-region): Fix docstring.
* helm-mode.el (helm--completion-in-region): Try to guess default value or require-match.
* helm-mode.el (helm--completion-in-region): Add source name and buffer.