ox: Ignore whitespace differences when resolving a radio link

* lisp/ox.el (org-export-resolve-radio-link): Ignore whitespace
  differences when resolving a radio link.
* testing/lisp/test-ox.el: Add test.
Merge branch 'maint'
org-table: several cleanups

* lisp/org.el (org-table-clean-did-remove-column),
  lisp/org-table.el (org-table-clean-did-remove-column): Move defvar,
  this dynamic variable is only used in org-table.
* lisp/org-table.el (org-table-colgroup-info): Remove unused defvar
  for `org-table-colgroup-info'.
  (org-table-clean-before-export): Let-bind regular expression strings
  and remove unused matching group.  Use
  `org-table-clean-did-remove-column' in cond statement rather than
  branching via if to avoid code duplication.  Remove the code
  associated with the removed `org-table-colgroup-info'.
  (orgtbl-export): Remove unused internal function.