Due to timing problem, test was not properly testing.
What needs to be ensured is:
   vgdb is attached (i.e. is ptracing valgrind)
   2 sigusr1 signals are sent while vgdb is ptracing
     vgdb will queue these signals
   when continuing, the queued signals are delivered.

With 3.9.0, the above causes an internal error in valgrind:
valgrind: m_syswrap/syswrap-main.c:1436 (vgPlain_client_syscall): Assertion 'sci->status.what == SsIdle' failed.

It would be better to have explicit synchronisation in the test
rather than counting on 'sleep xxx' to have things done in the
order that tests the signal queueing.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13910 a5019735-40e9-0310-863c-91ae7b9d1cf9
Improve the comments in the test


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13911 a5019735-40e9-0310-863c-91ae7b9d1cf9
Make the test (more) deterministic by having send_signal using
a guardcmd before sending the signal.
This allows to be sure that the signal are emitted when vgdb
is attached.
We still have one 'sleep' in the test.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13912 a5019735-40e9-0310-863c-91ae7b9d1cf9