runtest cmd line args. Fixes #42

runtest can now parse command line arguments using argtable2. It is possible to run specific test suites (eg : util + commandline) or a specific test in a specific suite (eg: "initialization" in the suite "core"). The  -f parameter causes the tests to run in forked mode and --help displays the help text.

argtable2 is available in debian (I use linux mint) repository (libargtable2) so I hope that won't be a problem.

However, I could not figure out a way to run specific tests from specific suites. For example, I cannot run selectively the tests "initialization" and "varnamc" from the suites "core" and "commandline" together (I can run all the tests in both core and util together though). argtable won't let me set both suite name and test name as parameters that can take variable number of arguments.