gdb_test_multiple match eof of any spawn_id

gdb_test_multiple match eof of any spawn_id

Since silent handling of eof is usually the wrong thing to do, this
patch makes gdb_test_multiple handle it for all $any_spawn_id.

Currently, against gdbserver, interrupt.exp occasionaly fails like
this:

 FAIL: gdb.base/interrupt.exp: send end of file

gdb.log with expect debug output enabled shows:

 expect: does "\r\n\r\nChild exited with status 0\r\nGDBserver exiting\r\n" (spawn_id exp8) match regular expression "end of file"? Gate "end of file"? gate=no
 expect: read eof
 expect: set expect_out(spawn_id) "exp8"
 expect: set expect_out(buffer) "\r\n\r\nChild exited with status 0\r\nGDBserver exiting\r\n"
 FAIL: gdb.base/interrupt.exp: send end of file

Note "expect: read eof" for spawn_id=exp8.  exp8 is
inferior_spawn_id/gdbserver_spawn_id.  That means
expect/gdb_test_multiple saw gdbserver exit before we got the expected
gdb output.  Since there's no explicit pattern for "eof", expect (and
thus gdb_test_multiple) just returns.

After this commit, we get instead:

 ERROR: Process no longer exists
 UNRESOLVED: gdb.base/interrupt.exp: send end of file

Note that before we still got an FAIL because $saw_inferior_exit is 0
when we get to:

	gdb_assert { $saw_eof && $saw_inferior_exit } $msg

Fixing the fail (now unresolved) will be the subject of a separate
patch.

gdb/testsuite/ChangeLog:
2015-04-23  Pedro Alves  <palves@redhat.com>

	* lib/gdb.exp (gdb_test_multiple): Match eof/full_buffer/timeout
	on $any_spawn_id instead of only on $gdb_spawn_id.