Forgot importing COMMON-LISP symbols into core.object.
Delete with-input-from-file & with-output-to-string.
Add add-package-local-nickname.
Add tests for add-package-local-nickname.
Allow to specify package-local-nicknames in defpackage.

Example:
  (defpackage test-package
    (:use :cl21
          (:foo.bar.baz :as :fbz)))
  (in-package :test-package)

  (fbz:hello)