[O] [ANN] Parsed keywords no longer hard-coded

[Nicolas Goaziou]

Hello,

Parser used to have a hard-coded list of keywords that should be parsed,
namely "TITLE", "DATE" and "AUTHOR". This is no longer the case since
export back-ends can explicitly introduce new parsed keywords (e.g.,
"SUBJECT" in "ox-koma-letter") with a `parse' behavior (see
`org-export-options-alist').

Note that if a keyword is parsed, its associated property (with prefix
"EXPORT_") will be, too. Macros are now expanded in any of them.

As a side-effect, `org-element-context', which shouldn't depend on
back-ends loaded, cannot return objects within "TITLE", "DATE" and
"AUTHOR". This shouldn't affect `org-open-at-point', which now follows
links within all keywords.


Regards,

-- 
Nicolas Goaziou                                                0x80A93738