Fix links with newline characters
* lisp/org-element.el (org-element-link-parser): Correctly parse links
with newline characters.
* lisp/org.el (org-make-link-regexps): Allow newline characters within
angle links.
(org-activate-angle-links): Support multiline angle links.
* testing/lisp/test-org-element.el (test-org-element/link-parser):
Update tests.
As a rule of thumb, any newline character and all surrounding
whitespaces are treated as a single space in a bracket link. They are
removed in angle links.