A trivial optimization and a formatting fix

* lisp/subr.el (internal--compiler-macro-cXXr): Re-use `head' for `n'.
Fix indentation and line length.

lisp/subr.el

@@ -540,12 +540,12 @@ i.e., subtract 2 * `most-negative-fixnum' from VALUE before shifting it."
 ;; you may want to amend the other, too.
 (defun internal--compiler-macro-cXXr (form x)
   (let* ((head (car form))
-         (n (symbol-name (car form)))
+         (n (symbol-name head))
          (i (- (length n) 2)))
     (if (not (string-match "c[ad]+r\\'" n))
         (if (and (fboundp head) (symbolp (symbol-function head)))
-            (internal--compiler-macro-cXXr (cons (symbol-function head) (cdr form))
-                                     x)
+            (internal--compiler-macro-cXXr
+             (cons (symbol-function head) (cdr form)) x)
           (error "Compiler macro for cXXr applied to non-cXXr form"))
       (while (> i (match-beginning 0))
         (setq x (list (if (eq (aref n i) ?a) 'car 'cdr) x))