(sexp_input_init): Initialize input->string

properly.
(sexp_get_char): Fixed non-transport case.
(sexp_get_quoted_char): Fixed default case.
(sexp_get_token): Loop over sexp_get_char (needed for handling of
white space). Don't modify input->level. Fixed the code that skips
comments.
(sexp_put_char): Fixed off-by-one bug in assertion.
(sexp_put_string): Fixed escape handling for output of quoted
strings.
(sexp_convert_list): Prettier output, hanging indent after the
first list element.
(sexp_skip_token): New function.
(sexp_convert_item): Use sexp_skip_token to skip the end of a
"[display-type]".

Rev: src/nettle/examples/sexp-conv.c:1.3