Introduce lib/util

util.[ch] contains functions used to control and check arguments for tests.

 - testname_set(const char *group, const char *subtest)
        set proper formated value to variable testname
 - assert_args(int num_args, int needed_args)
        check if test gets enough arguements and print error message and abort if not.
 - testname
        global variable usable for report function