`rb_file_const` is not working

In dir.c, `rb_file_const` is used to define constants in static `rb_mFConst` in file.c.

```C
    rb_file_const("FNM_NOESCAPE", INT2FIX(FNM_NOESCAPE));
```

`RDoc::Parser::C#do_constants` scans this line, but `RDoc::Parser::C#gen_const_table` does not support `rb_file_const` and the document for this line is ignored.

Ditto for `rb_curses_define_const`.