Fix asn1c warnings.
The strategy is rather basic. Files with warnings are replaced by an edited copy that triggers no warning. We take care to check that the replaced file is the same as the one that was analyzed at the time of warning removal (through checking its SHA1). There is a new bash script "fix_asn1" in cmake_targets/tools and the files replacing the existing ones are in cmake_targets/tools/fix_asn1.data.