org.el: Various fixes to the org-goto interface

org.el: Various fixes to the org-goto interface

* org.el (org-goto-auto-isearch): Enhance docstring.
(org-goto-map): Make a defun, so that the customized value of
org-goto-auto-isearch is correctly initialized.
(org-goto): Initialize the keymap with `org-goto-map'.
(org-get-location): Use *Org Help* as a temporary buffer.
Tell whether auto-isearch is on or off.

Thanks to Tyler Smith for reporting this.