fix duplicates.

C/signals.c

@@ -40,9 +40,6 @@ static char     SccsId[] = "%W% %G%";
 #include <tracer.h>
 #endif
 
-#ifndef THREADS
-#define worker_id 0
-#endif
 
 /*
  * The InteractSIGINT function is called after a normal interrupt had been caught.

C/sysbits.c

@@ -1538,9 +1538,6 @@ static RETSIGTYPE
 ReceiveSignal (int s, void *x, void *y)
 {
   CACHE_REGS
-#ifndef THREADS
-#define worker_id 0
-#endif
   LOCAL_PrologMode |= InterruptMode;
   my_signal (s, ReceiveSignal);
   switch (s)