There is always a thread

[Andrew Cagney <ac131313 at redhat dot com>]

(Goes nicely with the `there is always a frame' dogma, but I've a patch 
for that one :-)

GDB contains the function:

void
load_infrun_state (ptid_t ptid, ...)
{
  struct thread_info *tp;

  /* If we can't find the thread, then we're debugging a single threaded
     process.  No need to do anything in that case.  */
  tp = find_thread_id (pid_to_thread_id (ptid));
  if (tp == NULL)
    return;

  *prev_pc = tp->prev_pc;
  *prev_func_start = tp->prev_func_start;
  *prev_func_name = tp->prev_func_name;
  *trap_expected = tp->trap_expected;
  ...;
}

where what is being modified (even though it's all nicely parameterized) 
are global variables (see "inferior.h").

Anywone interested in trying to change this so that, instead, it assumes 
that `there is always a thread' and hence, not constantly swap thread 
and global variables.

Andrew