[MPlayer-dev-eng] make clean and make distclean behavior

[Diego Biurrun]

So our behavior on make clean and make distclean is somewhat
non-standard - *surprise* ...

distclean is recursive while clean is not and distclean does not remove
all generated files, config.h and config.mak get left behind.

I think there was a reason for this behavior back in the day, but, for
the life of me, I cannot remember it - if I ever knew.

So is there any reason nowadays to keep things as they are?  I think I
want to have a bit more standard semantics with recursive clean and a
distclean that returns pristine sources.

Diego