remove asn1 compilation fixes that went to asn1c (IMPORTANT: reinstall asn1c!)

The files NativeInteger.c.diff and constr_SET_OF.c.diff
from asn1c were generating compilation warnings. We had
local patches applied on generated files by asn1c.

A new version of asn1c has been pushed to
https://gitlab.eurecom.fr/oai/asn1c
(commit 224dc1f991b7e7ad705ce92e171b942f87b7b7e7)
making obsolete the fixes we do here.

So we now remove those fixes.

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* IMPORTANT BEGIN       *
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Everyone should update their asn1c installation.

The simplest is to do:

    source oaienv
    cd cmake_targets
    ./build_oai -I

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* IMPORTANT END         *
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