README: Fix AppVeyor branch and add link to LICENSE

Point AppVeyor status badge to master

Closes GH-4763.

[ci skip]

Author: gerardroche

README.md

@@ -11,11 +11,11 @@
 
 PHP is a popular general-purpose scripting language that is especially suited to
 web development. Fast, flexible and pragmatic, PHP powers everything from your
-blog to the most popular websites in the world. PHP is distributed under the PHP
-License v3.01.
+blog to the most popular websites in the world. PHP is distributed under the
+[PHP License v3.01](LICENSE).
 
 [![Build status](https://travis-ci.org/php/php-src.svg?branch=master)](https://travis-ci.org/php/php-src)
-[![Build status](https://ci.appveyor.com/api/projects/status/meyur6fviaxgdwdy?svg=true)](https://ci.appveyor.com/project/php/php-src)
+[![Build status](https://ci.appveyor.com/api/projects/status/meyur6fviaxgdwdy/branch/master?svg=true)](https://ci.appveyor.com/project/php/php-src)
 [![Build Status](https://dev.azure.com/phpazuredevops/php/_apis/build/status/php.php-src?branchName=master)](https://dev.azure.com/phpazuredevops/php/_build/latest?definitionId=1&branchName=master)
 
 ## Documentation