Move ISASCII defination to parse.y

[S-H-GAMELINKS]

Move to ISASCII defination to parse.y for universal parser.

[yui-knk]

Thanks for the PR. Can I ask you to update check these points?

1. Remove int (*isascii)(int c); from struct rb_parser_config_struct (rubyparser.h) then remove config->isascii = parse_isascii; from rb_parser_config_initialize (ruby_parser.c). One of goals of the refactoring is to minimize the number of functions required by rb_parser_config_t.
2. Define parse_isascii in parse.y not rubyparser.h. rubyparser.h is a public interface. I don't want to make parse_isascii public. We can put parse_isascii definition just before #ifdef ISASCII in parse.y

[S-H-GAMELINKS]

Thanks for your review!
I fixed these point.

1. Remove int (*isascii)(int c); from struct rb_parser_config_struct (rubyparser.h) then remove config->isascii = parse_isascii; from rb_parser_config_initialize (ruby_parser.c). One of goals of the refactoring is to minimize the number of functions required by rb_parser_config_t.
2. Define parse_isascii in parse.y not rubyparser.h. rubyparser.h is a public interface. I don't want to make parse_isascii public. We can put parse_isascii definition just before #ifdef ISASCII in parse.y

[yui-knk]

Thank you!