avoided compilation warnings on gcc 3.3.x systems

ChangeLog

asn1c/tests/check-assembly.sh

configure.in

skeletons/BOOLEAN.c

skeletons/INTEGER.c

skeletons/NativeInteger.c

skeletons/OBJECT_IDENTIFIER.c

skeletons/OCTET_STRING.c

skeletons/RELATIVE-OID.c

skeletons/ber_decoder.c

skeletons/ber_tlv_length.c

skeletons/ber_tlv_tag.c

skeletons/constr_CHOICE.c

skeletons/constr_SEQUENCE.c

skeletons/constr_SET.c

skeletons/constr_SET_OF.c