Parameter passing issue in Prepare2 for WinRT

[rigdern]

• The marshaling for the sql parameter should be switched from UnmanagedType.LPStr to UnmanagedType.LPWStr (source).
• Here and here the Prepare2 calls should pass -1 rather than query.Length to match the implementations on the other platforms (that parameter expects a number of bytes and I'm not sure using query.Length returns the correct result).

I believe this fix was already done for all platforms including WinRT in commit 1c2b3c0. However, it looks like there was a conflict with commit 77662f8 and the WinRT fix was partially lost.

Adam Comella
Microsoft Corp.