Add documentation about compiling the tests
Fix a few typos
Move optstring to a constant
Fix a memory leak in child process
Add option to silence output

So far this works by opening /dev/null and substituting it for standard
output.
Implement -q in a better way

Instead of relying on /dev/null, mark the setting in a global structure
and if the run is quiet, do not print progress and copy the log. This
way also does not need more system calls.
Update documentation
Drop global structure

Instead use an argument to ut_run_all_tests().
Update documentation