Fix build by defining more routines used by XTLDR

sdk/xtdk/i686/arfuncs.h

@@ -20,10 +20,18 @@ XTCDECL
 VOID
 ArClearInterruptFlag();
 
+XTCDECL
+BOOLEAN
+ArCpuId(IN OUT PCPUID_REGISTERS Registers);
+
 XTCDECL
 VOID
 ArHalt();
 
+XTCDECL
+ULONG_PTR
+ArReadControlRegister(IN USHORT ControlRegister);
+
 XTCDECL
 VOID
 ArWriteControlRegister(IN USHORT ControlRegister,