Make raising and lowering not mess up table alignment

Make raising and lowering not mess up table alignment

* lisp/org-compat.el (org-string-match-p):
(org-looking-at-p): New functions.
* lisp/org-table.el (org-table-align): Handle raised text with
invisible characters.
* lisp/org.el (org-script-display): Add raise properties for tables.
(org-raise-scripts): Handle raising differently inside tables.

Pretty display of subscripts and superscripts no longer messes up
table alignment.  This is achieved by two things:

1. Inside tables, the raised characters are not made smaller, they
   remains at the same size.  Instead they are raise/lowered more, by
   a full half character height to still be clearly readable as
   subscript or superscript.

2. The invisible characters are taken into account when computing the
   field width.