Remove OrgStruct mode
* lisp/org.el (org-overview): Use `org-outline-regexp-bol' instead of
`outline-regexp'.
(org-heading-components): Ignore orgstruct-mode.
(orgstruct-heading-prefix-regexp):
(orgstruct-setup-hook):
(org-local-vars):
(orgstruct-mode):
(turn-on-orgstruct):
(orgstruct-is-++):
(org-fb-vars):
(orgstruct++-mode):
(turn-on-orgstruct++):
(orgstruct-error):
(orgstruct-setup):
(orgstruct-make-binding):
(org-run-like-in-org-mode):
(org-indent-line):
(org-fill-paragraph):
(org-show-children): Remove Orgstruct mode
* doc/org.texi (Orgstruct mode): Remove node.