This compatibility is mainly re-instored for convenience of user to
style the fonts used for the caption, and also possibly influence the
horizontal position via "width" or "margin" option of caption package
(attention that caption package obeys the document class tacit "twoside"
option, so if left and right margins are not set-up to be the same,
positioning of caption will depend on parity of the page number).
Regarding vertical skips, for captions placed on top (which is the table
templates default and also the literalblockcappos default), this commit
ensures that the vertical spacing separating the caption last baseline
to the top of framing is governed by \sphinxbelowcaptionspace in all
these three cases: tabular(y), longtable, literal blocks; the "skip"
option of caption package is ignored for them.
The "skip" is obeyed for the spacing between an image and its caption,
which currently in Sphinx is always below the image (no customization of
the figure caption vertical placement is currently available).
If literalblockcappos is "b" (captions follow code-blocks), this commit
removes the caption-package added \abovecaptionskip, so that "skip" is
also ignored for code-blocks in this case. This looks better due to the
extra space already added by the framing of the code-block and achieves
same spacing as without caption package (presumably loaded mainly to
style the fonts used for the caption). However in future maybe caption's
package "skip" should be obeyed for "literalblock" caption type.
Fixes: 5520
This implementation in latex writer allows arbitrary columns to be
declared "stub columns". But currently Docutils option
``:stub-columns:`` only allows a number telling the how many initial
columns are "stub columns".
