Allow spaces around "=" in code block variable specifications

* lisp/ob.el (org-babel-join-splits-near-ch): Rejoins a list of a
  split string when a character appears on either side of the split.
  (org-babel-parse-multiple-vars): Rejoin splits around "=" signs.

lisp/ob.el

@@ -1151,6 +1151,18 @@ instances of \"[ \t]:\" set ALTS to '((32 9) . 58)."
 	    (string-to-list string))
       (nreverse (cons (apply #'string (nreverse partial)) lst)))))
 
+(defun org-babel-join-splits-near-ch (ch list)
+  "Join splits where \"=\" is on either end of the split."
+  (flet ((last= (str) (= ch (aref str (1- (length str)))))
+         (first= (str) (= ch (aref str 0))))
+    (reverse
+     (org-reduce (lambda (acc el)
+               (let ((head (car acc)))
+                 (if (and head (or (last= head) (first= el)))
+                     (cons (concat head el) (cdr acc))
+                   (cons el acc))))
+             list :initial-value nil))))
+
 (defun org-babel-parse-header-arguments (arg-string)
   "Parse a string of header arguments returning an alist."
   (when (> (length arg-string) 0)
@@ -1179,7 +1191,8 @@ shown below.
     (mapc (lambda (pair)
 	    (if (eq (car pair) :var)
 		(mapcar (lambda (v) (push (cons :var (org-babel-trim v)) results))
-			(org-babel-balanced-split (cdr pair) 32))
+			(org-babel-join-splits-near-ch
+			 61 (org-babel-balanced-split (cdr pair) 32)))
 	      (push pair results)))
 	  header-arguments)
     (nreverse results)))

testing/lisp/test-ob.el

@@ -497,6 +497,13 @@ on two lines
     (org-babel-next-src-block 3)
     (should (equal (org-babel-execute-src-block) "foo"))))
 
+(ert-deftest test-ob/allow-spaces-around-=-in-var-specs ()
+  (org-test-with-temp-text "#+begin_src emacs-lisp :var a = 1 b = 2 c= 3 d =4
+  (+ a b c d)
+#+end_src
+"
+    (should (= 10 (org-babel-execute-src-block)))))
+
 (provide 'test-ob)
 
 ;;; test-ob ends here