msiexec: add /unreg as an alias for /z

[Austin English]

TurboTax 2010 uses this.

-- 
-Austin
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diff --git a/programs/msiexec/msiexec.c b/programs/msiexec/msiexec.c
index 70e3255..8551e00 100644
--- a/programs/msiexec/msiexec.c
+++ b/programs/msiexec/msiexec.c
@@ -563,7 +563,8 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
 		{
 			FunctionRegServer = TRUE;
 		}
-		else if (msi_option_equal(argvW[i], "unregserver") || msi_option_equal(argvW[i], "unregister"))
+		else if (msi_option_equal(argvW[i], "unregserver") || msi_option_equal(argvW[i], "unregister") 
+			||  msi_option_equal(argvW[i], "unreg"))
 		{
 			FunctionUnregServer = TRUE;
 		}