msi: Write-strings warnings fix

[Mike McCormack]

Andrew Talbot wrote:

> MSI{Get|Set}FeatureState(), MSI{Get|Set}ComponentState() and
> MSI{Get|Set}Property() have appropriate const string arguments in the SDK.

Which version of the Windows SDK is that?

> -UINT WINAPI MsiGetFeatureStateA(MSIHANDLE hInstall, LPSTR szFeature,
> +UINT WINAPI MsiGetFeatureStateA(MSIHANDLE hInstall, LPCSTR szFeature,
>                    INSTALLSTATE *piInstalled, INSTALLSTATE *piAction)

According to my version of the Windows SDK, these changes are wrong.

Mike