gdb.python/py-events.exp and normal_stop observers ordering

gdb.python/py-events.exp and normal_stop observers ordering

I have patches that:

 1 - make the CLI print stop info from a normal_stop observer, like MI
     does.

 2 - happen to change the order in which the Python and CLI/TUI
     normal_stop observers are installed.

With those in place, py-events.exp regresses like shown below [1],
because the Python stop events are output before CLI prints stop info,
instead of after, and the test doesn't expect that.

With the same Python hooks, the order in which MI and Python events is
emited today is already undefined, because MI also uses the
normal_stop observer for output.  I see no reason that we should in
general define the order observers, interpreters and scripting
languages get their turn at being notified of these events.  So this
patch makes the test cope with Python->CLI output order too.

Tested on x86_64 Fedora 20.

gdb/testsuite/
2015-07-24  Pedro Alves  <palves@redhat.com>

	* gdb.python/py-events.exp: Accept output between the stop event
	and the prompt.
	* gdb.python/py-evsignal.exp: Likewise.
	* gdb.python/py-evthreads.exp: Likewise.

[1] - The regressions in question look like:

Before said patches:
  (gdb) continue
  Continuing.
  event type: continue

  Breakpoint 2, first () at /home/pedro/gdb/mygit/build/../src/gdb/testsuite/gdb.python/py-events.c:30
  30	  for (i = 0; i < 2; i++)
  event type: stop
  event type: stop
  stop reason: breakpoint
  first breakpoint number: 2
  breakpoint number: 2
  breakpoint number: 3
  all threads stopped
  (gdb) PASS: gdb.python/py-events.exp: continue

After said patches:
  (gdb) continue
  Continuing.
  event type: continue
  event type: stop
  event type: stop
  stop reason: breakpoint
  first breakpoint number: 2
  breakpoint number: 2
  breakpoint number: 3
  all threads stopped

  Breakpoint 2, first () at /home/pedro/gdb/mygit/build/../src/gdb/testsuite/gdb.python/py-events.c:30
  30	  for (i = 0; i < 2; i++)
  (gdb) FAIL: gdb.python/py-events.exp: continue