build-sys: Enable testing of sigqueue

build-sys: Enable testing of sigqueue

The referenced commits enavled both pkill and kill to send an integer to
the killed or signalled process. The test_process now will report on the
integer if sent and the testsuite changes take advantage of this
new feature.

Another process make/destroy set had to be made as using spawn
instead of exec changes both the SID and TTY for the underlying
process, making other tests fail.

References:
 commit 7d55409b82602dac540c011000c9c5abedb5158a
 commit 2b804a532a90a98bccc5255a728da9076a5e4f4f