Incomplete: Various fixes

* Empty fragment encoding
* Dereference DEFAULT to get the actual value
* Don't write length bits for small fixed-sized sequence-of
* Index encoding in choice extensions
* Only align when range == 256

converter-example.c.

They're disabled by default, but can be turned on by defining USE_OLDER_APER_NSNNWN.
The main difference is - these do not use "range" argument, but receive it as dummy.

    In some cases an INTEGER overflow during parsing is not detected
    and incorrect value is returned to the decoder instead of an error.
    Reported by Nika Pona <npona@digamma.ai>.
    (Severity: low; Seuciry impact: medium).

Fix compiler redefinition warnings for __EXTENSIONS__

per_support: use intmax_t for integer constraints

long causes trouble on 32bit systems, see https://github.com/riebl/vanetza/issues/78

Fix for 32bit crossdev environment tests

* tests using readdir and other
  filesystem related functions fail
  when using 32bit crossdev
  environment without these changes