* mes.c (function_t): New struct.
(type): One type for function.
(call): Refactor.
* build-aux/mes-snarf.mes: Use arity annotation. WAS: args. Update
annotations.
* mes.c (scm_t): Add string field.
(make_string, internal_lookup_symbol, internal_make_symbol,
make_symbol, lookup, readword): Take scm*. Update callers.
(display_helper): Support string field.
(append_char): New function.
(readstring): Use it. Produce scm*.
(cstring_to_list): New function.
(add_environment, internal_make_symbol): Use it.
(list_of_char_equal_p): New function.
(internal_lookup_symbol): Use it.
* lib.c (list_ref): New function.
* string.c (string_ref): Use it.
(string, string_append, string_length, substring, number_to_string,
string_to_symbol, symbol_to_string): Update to list-of-characters
implementation.
