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

This commit fixes all copyright notes, using "git blame" as a
reference.  For simple files I just added a 2-lines boilerplate about
being WR and GPL.

Some parts I left untouched:

  trivial-init and related files (unclear to me what this is,
  and pf-microcode.h is magic binary pfilter values).

  tools/lm32-etheruart: I don't know what this is and who the author is

  libsdbfs: this comes from another repo and I'd better not change it

  sfp_lib.h and hal_shmem.h: I lost track about the origin of this,
  among the several packages.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

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

This time I added -Wmissing-prototypes and fixed accordingly. Again, this
used to be part of -Wall and I'm disgusted by it not being so any more.

What does "all" mean, then?
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

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

We don't want to call the real printf, which brings in the whole of
newlib, but it sometimes happen. So let's diagnose the problem
immediately rather than letting users wonder what is wrong with the
size.

Similarly, if building under ppsi, ensure we are not calling libgcc
division functions: any 64-bit division my be done with __div64_32
offered by ppsi/lib (copied from the kernel).
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>