Always add sitemap file to project files if sitemap is requested

* lisp/org-publish.el (org-publish-get-base-files): Add sitemap file.

I noticed some wonkiness in getting my sitemap created on my webserver
when pushing my website, and the problem seems to lie in
org-publish-get-base-files only returning existing files, and not
picking up on the soon to be generated sitemap. My patch always adds
the sitemap file to the list of returned files if a sitemap is
requested, regardless of if it exists or not.

lisp/org-publish.el

@@ -434,6 +434,9 @@ matching filenames."
 	 ;; org-publish-compare-directory-files:
 	 (sitemap-requested
 	  (plist-get project-plist :auto-sitemap))
+	 (sitemap-filename
+	  (or (plist-get project-plist :sitemap-filename)
+	      "sitemap.org"))
 	 (sitemap-sort-folders
 	  (if (plist-member project-plist :sitemap-sort-folders)
 	      (plist-get project-plist :sitemap-sort-folders)
@@ -454,6 +457,9 @@ matching filenames."
       (setq sitemap-sort-folders nil))
 
     (setq org-publish-temp-files nil)
+    (if sitemap-requested
+	(pushnew (expand-file-name (concat base-dir sitemap-filename))
+		  org-publish-temp-files))
     (org-publish-get-base-files-1 base-dir recurse match
 				  ;; FIXME distinguish exclude regexp
 				  ;; for skip-file and skip-dir?