ox-latex.el: support sideways :float options for tables and figures

* lisp/ox-latex.el (org-latex--inline-image): support a 'sideways
option for the float, and add case to handle it with a \sideaysfigure
in the export.
(org-latex--org-table): support "sideways" instead of deprecated
"sidewaystable".  The latter is still handled for backward
compatibility.

* doc/org.texi (Tables in LaTeX export): Document use of :float
  sideways.
(Images in LaTeX export): Document use of :float sideways.

This patch provides consistent :float sideways support for LaTeX
export of both figures and tables.

http://permalink.gmane.org/gmane.emacs.orgmode/84618

TINYCHANGE

doc/org.texi

@@ -11696,10 +11696,13 @@ task, you can use @code{:caption} attribute instead.  Its value should be raw
 @LaTeX{} code.  It has precedence over @code{#+CAPTION}.
 @item :float
 @itemx :placement
-Float environment for the table.  Possible values are @code{sidewaystable},
+The @code{:float} specifies the float environment for the table.  Possible
+values are @code{sideways}@footnote{Formerly, the value was
+@code{sidewaystable}.  This is deprecated since Org 8.3.},
 @code{multicolumn}, @code{t} and @code{nil}.  When unspecified, a table with
-a caption will have a @code{table} environment.  Moreover, @code{:placement}
-attribute can specify the positioning of the float.
+a caption will have a @code{table} environment.  Moreover, the
+@code{:placement} attribute can specify the positioning of the float.  Note:
+@code{:placement} is ignored for @code{:float sideways} tables.
 @item :align
 @itemx :font
 @itemx :width
@@ -11802,6 +11805,11 @@ environment.
 @code{wrap}: if you would like to let text flow around the image.  It will
 make the figure occupy the left half of the page.
 @item
+@code{sideways}: if you would like the image to appear alone on a separate
+page rotated ninety degrees using the @code{sidewaysfigure}
+environment.  Setting this @code{:float} option will ignore the
+@code{:placement} setting.
+@item
 @code{nil}: if you need to avoid any floating environment, even when
 a caption is provided.
 @end itemize

lisp/ox-latex.el

@@ -1801,6 +1801,7 @@ used as a communication channel."
 	 (float (let ((float (plist-get attr :float)))
 		  (cond ((and (not float) (plist-member attr :float)) nil)
 			((string= float "wrap") 'wrap)
+			((string= float "sideways") 'sideways)
 			((string= float "multicolumn") 'multicolumn)
 			((or float
 			     (org-element-property :caption parent)
@@ -1876,6 +1877,10 @@ used as a communication channel."
 \\centering
 %s%s
 %s\\end{wrapfigure}" placement comment-include image-code caption))
+      (sideways (format "\\begin{sidewaysfigure}
+\\centering
+%s%s
+%s\\end{sidewaysfigure}" comment-include image-code caption))
       (multicolumn (format "\\begin{figure*}%s
 \\centering
 %s%s
@@ -2547,7 +2552,8 @@ This function assumes TABLE has `org' as its `:type' property and
 		      (let ((float (plist-get attr :float)))
 			(cond
 			 ((and (not float) (plist-member attr :float)) nil)
-			 ((string= float "sidewaystable") "sidewaystable")
+			 ((or (string= float "sidewaystable")
+			      (string= float "sideways")) "sidewaystable")
 			 ((string= float "multicolumn") "table*")
 			 ((or float
 			      (org-element-property :caption table)