Use `string=' to compare strings

* org-elisp-symbol.el (org-elisp-symbol-store-link): Use `string=' to
compare strings.

(let ((foo "foo"))
  (eq foo "foo")) => nil

contrib/lisp/org-elisp-symbol.el

@@ -104,8 +104,8 @@
 	     (stype (cond ((commandp sym-name) "Command")
 			  ((functionp sym-name) "Function")
 			  ((user-variable-p sym-name) "User variable")
-			  ((eq def "defvar") "Variable")
-			  ((eq def "defmacro") "Macro")
+			  ((string= def "defvar") "Variable")
+			  ((string= def "defmacro") "Macro")
 			  (t "Symbol")))
 	     (args (if (match-string 3)
 		       (mapconcat (lambda (a) (unless (string-match "^&" a) a))