Enable Windows Update service on AppVeyor

The `php` Chocolatey package depends on `KB2919442` which isn't installed
on AppVeyor, and thus attempts to install it. This was failing as it
requires the Windows Update process to be running properly. This forces
that to be enabled.

appveyor.yml

@@ -9,6 +9,8 @@ branches:
 install:
   - cinst -y OpenSSL.Light
   - SET PATH=C:\Program Files\OpenSSL;%PATH%
+  - sc config wuauserv start= auto
+  - net start wuauserv
   - cinst -y php
   - cd c:\tools\php
   - copy php.ini-production php.ini