r8520: fixed a pile of warnings from the build farm gcc -Wall output on

r8520: fixed a pile of warnings from the build farm gcc -Wall output on
S390. This is an attempt to avoid the panic we're seeing in the
automatic builds.

The main fixes are:

 - assumptions that sizeof(size_t) == sizeof(int), mostly in printf formats

 - use of NULL format statements to perform dn searches.

 - assumption that sizeof() returns an int
(This used to be commit a58ea6b3854973b694d2b1e22323ed7eb00e3a3f)