Adapt forach iterator

The protocol of the foreach iterator macro is changed.
The "typedef node_t iteratedtype_containertype"
now must be defined as "typedef node_t * iteratedtype_containertype".
This allows wbuffer_t to iterate over 'memblock_t'
instead over (memblock_t*).
Add static check: '=' not used in TEST macro

All static tests are executed from
'C-kern/test/run_statictest.sh'.
Try integrate instream_t into utf8reader_t

utf8reader_t now uses instream_t and instream_mmfile_t_
adapter to read files.

The single buffer constraint is not yet removed.
Only function initsinglebuffer_utf8reader works.
init_utf8reader returns ENOSYS.

The integration showed that instream_t, instream_factory_t,
and adapter objects for different kinds of input channels
is too complex to maintain.

==> Implement a new concept and remove instream_t and support objects.