Transfer setf definitions if any in abbr.

[jcguu95]

This commit supports the macro abbr to transfer setf definitions for the function long to the abbreviated function short.

Provide two tests as well. Here's how you test:

(should-test:test :package 'rutils.test)

It resolves the issue(s): #63 .

;;; Example usage
(setf (rutil:lt (rutil:pair 0 0)) 1) ; => 1
(setf (rutil:rt (rutil:pair 0 0)) 1) ; => 1

---

Tested with

(should-test:test :package (find-package :rutils.test))
(should-test:test :package (find-package :rtl)) ; 5 failures, but those are presented in the master  branch already.