* lisp/net/browse-url.el: Turn on lexical-binding.
(browse-url--mailto, browse-url--man, browse-url--browser): Use
imperative form in docstrings.
(browse-url-delete-temp-file): Turn comment into a proper docstring.
* test/lisp/net/browse-url-tests.el: New file with tests for
browse-url.el.
