appveyor.yml in win32-security-0.4.1 vs appveyor.yml in win32-security-0.5.0

@@ -28,9 +28,11 @@
 
     if ((test-path $tpath) -eq $True){ rm -recurse -force $tpath }
 
     gem update --system > $null
 
+    if ((gem query -i ffi-win32-extensions) -eq $False){ gem install ffi-win32-extensions --no-document }
+
     if ((gem query -i sys-admin) -eq $False){ gem install sys-admin --no-document }
 
     if ((gem query -i test-unit -v ">= 3.0") -eq $False){ gem install test-unit --no-document }
 cache:
 - C:\Ruby193\lib\ruby\gems\1.9.1