skip kill test too if running runtest

I find more readable instead of make check to run
cd testsuite && make site.exp && DEJAGNU=global-conf.exp runtest

But in that case, kill.exp was still trying to run with
ERROR: tcl error sourcing ./kill.test/kill.exp.
ERROR: couldn't execute "/usr/src/procps-ng-3.3.7/kill": no such file or
directory
...

Simply return from test if kill is not build

Signed-off-by: Gilles Espinasse <g.esp@free.fr>
procps-ng : tests, remove which dependency

which is a separate package that may not be available and is not yet build on Linux from scratch build order.
Instead use posix command -v. command -v  is a builtin working with bash-4.2, 3.0.25 or even old bash-2.05 or current debian dash

Signed-off-by: Gilles Espinasse <g.esp@free.fr>
procps-ng testsuite : simplify DEJAGNU workaround

No need to distribute an empty file
/dev/null is enought to silent global config file warning

Signed-off-by: Gilles Espinasse <g.esp@free.fr>
3.3.8 NEWS and API

NEWS mentions systemd unit support for ps

Library REVISION (internal change only) incremented

Signed-off-by: Craig Small <csmall@enc.com.au>
Merge branch 'master' of git://gitorious.org/procps/procps