* check if __EXTENSIONS__ if alreay
  defined

The encode function call will crash if it's not initialized. Update the document to make it more clear.

by Krzysztof Witek <kwitek@kw-net.com> vlm/asn1c d3dbe60400f80c91

Also, for the record. The following commits from vlm/asn1c PR #115 were
already suggested and merged here in the past:
- work in 128-bit integer values while compiling f49ee68bcb
- aper: use correct function for APER decoder    0abceb4382fee19c4
- aper: fix invalid read                         d158c573fb762857a

commit vlm/asn1c e9e346064b67a0946

Committed "aper: workaround for undefined enumeration indexes" by Krzysztof Witek <kwitek@kw-net.com>
commit a12c7fa47901bf6dee4cc21702efa6e7ecc1bb4f from vlm/asn1c #115

This fixes lots of typos that end up in the generated output, possibly
in other projects, which would then be unable to fix these typos as they
will reappear when running asn1c again.

Warned-by: codespell

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