Use the Unicode Win32 APIs

[saurabh500]

Ref: https://github.com/tvrprasad/sspi-client/blob/master/src_native/sspi_impl.cpp#L197

The code uses APIs like InitializeSecurityContextA and AcquireCredentialsHandleA
These are ANSI APIs and should be replaced with Unicode APIs

Ref: https://msdn.microsoft.com/en-us/library/ff381407.aspx

These changes will also allow support for IDN connectivity to Sql Server.