Remove configuration preprocessor symbols 'THREAD'

and 'THREAD_SAFE_CLIENT'.
  
As of MySQL 5.5, we no longer support non-threaded
builds.   This patch removes all references to the
obsolete THREAD and THREAD_SAFE_CLIENT preprocessor
symbols.  These were used to distinguish between
threaded and non-threaded builds.

dbug/dbug_analyze.c

@@ -571,12 +571,10 @@ int main (int argc, char **argv)
     FILE *infile;
     FILE *outfile = {stdout};
 
-#ifdef THREAD
 #if defined(HAVE_PTHREAD_INIT)
   pthread_init();                       /* Must be called before DBUG_ENTER */
 #endif
-  my_thread_global_init();
-#endif /* THREAD */
+  my_thread_global_init(); 
   {
     DBUG_ENTER ("main");
     DBUG_PROCESS (argv[0]);