* parser-defs.h (operator_length): Declare.

* parse.c (length_of_subexp): Use operator_length to get operator
lengths and arities for operators.
Move most code to new operator_length function.
(operator_length): New function absorbing most code from
length_of_subexp.
(prefixify_subexp): Remove large case and use operator_length instead.
(parse_exp_1): Use renamings:
dump_prefix_expression => dump_raw_expression and
dump_postfix_expression => dump_prefix_expression.

* expression.h (dump_prefix_expression): Rename to ...
(dump_raw_expression): New name.
(dump_postfix_expression): Rename to ...
(dump_prefix_expression): New name.

* expprint.c (dump_subexp): Make global.  Add comment.
Move most existing code to dump_subexp_body.
(dump_subexp_body): New function.
(dump_prefix_expression): Rename to dump_raw_expression.
Remove attempt to print the expression via print_expression: it can't
work before the expression is prefixified.
(dump_raw_expression): Renamed from dump_prefix_expression.
(dump_postfix_expression): Rename to dump_prefix_expression, since
that's what it does.
Remove 'note' parameter, since this routine must be used on
prefixified expression.
(dump_prefix_expression): Renamed from dump_postfix_expression.