NtQuerySystemInformation:
- Windows Vista and later: Check the information class before probing the buffer.
- Pre-Vista Windows: Check the information class after probing the buffer.
- Pre-Vista Windows: Fixed the aligment check for invalid information classes.
- Pre-Vista Windows: The SystemFlagsInformation and SystemKernelDebuggerInformation classes return no required length in case of an error.
This fixes all ntdll_apitest:NtSystemInformation fails.