Expect for "@" when doing "complete break ada" on gdb.ada/complete.exp

Expect for "@" when doing "complete break ada" on gdb.ada/complete.exp

Currently, gdb.ada/complete.exp's "complete break ada" test fails
because the regexp used to match the command's output doesn't expect
"@", but we have an output like:

  ...
  complete break ada
  break ada.assertions.assert
  break ada.calendar.arithmetic.difference
  break ada.calendar.arithmetic_operations.add
  break ada.calendar.arithmetic_operations.add.cold
  break ada.calendar.arithmetic_operations.add@plt
  break ada.calendar.arithmetic_operations.difference
  break ada.calendar.arithmetic_operations.difference@plt
  ...

This patch adds "@" to the regexp, unbreaking the test.

OK?

gdb/testsuite/ChangeLog:
2018-09-18  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.ada/complete.exp: Expect for "@" when doing "complete
	break ada".