Split `org-emph-re' and `org-verbatim-re'
* lisp/org.el (org-set-emph-re): Refactor code. Rip "~" and "="
markers off `org-emph-re'.
(org-do-emphasis-faces):
(org-sort-remove-invisible): Handle both `org-emph-re' and
`org-verbatim-re'.
(org-in-verbatim-emphasis): Use `org-verbatim-re' instead of
`org-emph-re'.
* lisp/org-element.el (org-element-code-parser):
(org-element-verbatim-parser): Use `org-verbatim-re' instead of
`org-emph-re'.
* testing/lisp/test-org-element.el (test-org-element/bold-parser):
(test-org-element/code-parser):
(test-org-element/italic-parser):
(test-org-element/strike-through-parser):
(test-org-element/underline-parser):
(test-org-element/verbatim-parser): Update tests, which no longer need
to bind `org-emph-re'.