msxml3: Use CP_UNIXCP instead of CP_ACP in libxmlFatalError as the input string is one generated by a native OS function.

widl: Raise RPC_X_SS_IN_NULL_CONTEXT exception for NULL in-only context handles instead of RPC_X_NULL_REF_PTR.

Based on a patch by Michael Martin.

Only supports the basic authentication scheme.

This part of the patch really has nothing to do with an idea the patch
aimed to achieve.