(die): New function.

(struct sexp_input): Deleted field ITEM.
(sexp_get_char): Die on failure, never return -1.
(sexp_get_quoted_char): Likewise.
(sexp_get_quoted_string): Die on failure, no returned value.
(sexp_get_base64_string): Likewise.
(sexp_get_token_string): Likewise.
(sexp_get_string): Likewise.
(sexp_get_string_length): Likewise.
(sexp_get_token): Likewise.
(sexp_convert_string): Adapted to sexp_get_token.
(sexp_convert_list): Likewise.
(sexp_convert_file): New function.
(main): Use sexp_convert_file.

Rev: src/nettle/examples/sexp-conv.c:1.4