Found by Valgrind.

Found by Valgrind.

Two issues here: item pointers array wasn't freed, root item data wasn't freed.
Found by Valgrind.

Fixes compilation on systems that don't support nameless unions or structs.

Found by Valgrind.

Found by Valgrind.

Found by Valgrind.

msi: The second parameter to Installer.OpenPackage is optional, so set a default value of 0 if the parameter is not provided.

It seems ugly to open up the parameters in pDispParams, but
DispGetParam will happily convert a VT_EMPTY to a VT_BSTR and not
return an error.

msi: It's possible to send in more than two parameters to Installer.OpenPackage, but sending in zero parameters should return DISP_E_TYPEMISMATCH.

The following series fixes a few leaks reported by valgrind.  We were
leaking exception info caused by Installer.OpenPackage failing when we
didn't expected it.