Implement HlHalt() intrinsic routine and add basic definitions for kernel services

sdk/xtdk/amd64/hlfuncs.h

@@ -22,6 +22,10 @@ XTAPI
 BOOLEAN
 HlCpuId(IN OUT PCPUID_REGISTERS Registers);
 
+XTAPI
+VOID
+HlHalt();
+
 XTAPI
 UCHAR
 HlIoPortInByte(IN USHORT Port);