Fix segfault for wrongly specified test on commandline.

[mbroz]

If explicitly specified test does not exist,
dieharder segfaults, for example
dieharder -d 42
dieharder -d 5000

[eddelbuettel]

Thanks for paying attention to that too. I long gave up on manually fiddling with argv[] and like getopt (from libc) or the wonderful (portable across languages) docopt.

[eddelbuettel]

Looks good to me!

[mbroz]

Thanks!
Docopt looks interesting, did not know about it!
But rewrite diehard CLI parsing is not so easy :-)

[eddelbuettel]

Yes -- retrofitting is harder. I meant more for newer projects.