Drop ZwQuerySystemInformation since NtQuerySystemInformation was
already available.
* fhandler_proc.cc (format_proc_uptime): Replace call to
ZwQuerySystemInformation by call to NtQuerySystemInformation.
(format_proc_stat): Ditto.
* fhandler_process.cc (format_process_stat): Replace call to
ZwQueryInformationProcess by call to NtQueryInformationProcess.
(get_process_state): Ditto.
(get_mem_values): Ditto. Replace call to ZwQueryVirtualMemory by
call to NtQueryVirtualMemory.
* ntdll.h: Cleanup. Drop ZwQuerySystemInformation since
NtQuerySystemInformation was already available. Replace declarations
of ZwXXX functions by declarations of NtXXX.
* pinfo.cc (winpids::enumNT): Replace call to ZwQuerySystemInformation
by call to NtQuerySystemInformation.