Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

3 are not enough: we need 4. So support up to 16 even though we waste
a few dozen bytes of precious RAM.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

we'd better err out than corrupt memory, if we have more arguments than
expected

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

dirname() and basename() change their argument.  We'd better
strdup(argv[0]) to be able to use it in error messages.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>