Primeira versão de alterações!

cls.h

#include <Windows.h>

void cls()
{
	COORD coordScreen = { 0, 0 };
	DWORD dwConSize,
	      cCharsWritten;
	CONSOLE_SCREEN_BUFFER_INFO csbi;

	if ( !GetConsoleScreenBufferInfo( GetStdHandle( STD_OUTPUT_HANDLE ), &csbi )) return;

	dwConSize = csbi.dwSize.X * csbi.dwSize.Y;

	if ( !FillConsoleOutputCharacter( GetStdHandle( STD_OUTPUT_HANDLE ), ( TCHAR )' ', dwConSize, coordScreen, &cCharsWritten )) return;
	if ( !GetConsoleScreenBufferInfo( GetStdHandle( STD_OUTPUT_HANDLE ), &csbi )) return;
	if ( !FillConsoleOutputAttribute( GetStdHandle( STD_OUTPUT_HANDLE ), csbi.wAttributes, dwConSize, coordScreen, &cCharsWritten )) return;
	SetConsoleCursorPosition( GetStdHandle( STD_OUTPUT_HANDLE ), coordScreen );
}