Revert "ob-tangle: no longer inserting newlines between appended code blocks"

This reverts commit 90f6765cdf77c1414726d899f00c77da43f45758.

lisp/ob-tangle.el

@@ -399,7 +399,7 @@ same name in the order they appear in the file."
 					     (cdr by-lang))))))
 			       (case org-babel-tangle-named-block-combination
 				 (append (mapconcat #'identity
-						    named ""))
+						    named "\n"))
 				 (first  (first named))
 				 (last   (car (last  named))))))
 			    (add-to-list 'tangled-names name))