lib/, src/: Use int main(void) where appropriate

lib/, src/: Use int main(void) where appropriate

Remove /*ARGSUSED*/ comments.  Instead, use appropriate declarators for
main().  ISO C allows using int main(void) if the parameters are going
to be unused.

Also, do some cosmetic changes in the uses of argc and argv, to show
where they are used.

And use *argv[], instead of **argv.  Array notation is friendlier, IMO.

Signed-off-by: Alejandro Colomar <alx@kernel.org>