ox: Speed-up some tools on tables
* lisp/ox.el (org-export-table-has-special-column-p): Tiny
refactoring.
(org-export-table-has-header-p): Fix cache use, i.e., no longer
re-compute return value when the table is already known to have no
header.
(org-export-table-row-group):
(org-export-table-row-number): Populate cache with all the rows
whenever a row is queried. This fixes previous quadratic behaviour.
Reported-by: Thierry Banel <tbanelwebmin@free.fr>
<http://permalink.gmane.org/gmane.emacs.orgmode/111131>