* lisp/org.el (org-completion-use-ido):
(org-completion-use-iswitchb):
(org-completion-fallback-command): Remove variables.
(org-refile):
(org-set-effort):
(org-read-property-value): Apply variables removal.
(org-iread-file-name): Make it an obsolete alias for `read-file-name'.
(org-file-complete-link): Use `read-file-name'.
(org-switchb): Remove unused function.
Completion mechanisms are expected to be handled at a lower level,
e.g. in `read-file-name-function'.
