Implement HlLoadTaskRegister() for loading TSS segment selector into task register

sdk/xtdk/amd64/hlfuncs.h

@@ -59,6 +59,10 @@ VOID
 HlIoPortOutLong(IN USHORT Port,
                 IN ULONG Value);
 
+XTCDECL
+VOID
+HlLoadTaskRegister(USHORT Source);
+
 XTCDECL
 ULONG_PTR
 HlReadControlRegister(IN USHORT ControlRegister);

sdk/xtdk/i686/hlfuncs.h

@@ -59,6 +59,10 @@ VOID
 HlIoPortOutLong(IN USHORT Port,
                 IN ULONG Value);
 
+XTCDECL
+VOID
+HlLoadTaskRegister(USHORT Source);
+
 XTCDECL
 ULONG_PTR
 HlReadControlRegister(IN USHORT ControlRegister);