* inferior.h, infrun.c, thread.c, infcmd.c: Remove all uses of

pc_changed.  If it was ever set to a non-zero value, it was before
	GDB 2.8.  It doesn't seem to have any useful function.

gdb/thread.c

@@ -187,7 +187,6 @@ thread_switch (pid)
     return;
 
   inferior_pid = pid;
-  pc_changed = 0;
   flush_cached_frames ();
   registers_changed ();
   stop_pc = read_pc();