mio 380ab02bb7 main/hypermail: fix build with gcc 15
Fix bool type and conflicting types errors.

```
In file included from date.c:28:
setup.h:4:13: error: 'bool' cannot be defined via 'typedef'
    4 | typedef int bool;
      |             ^~~~
setup.h:4:13: note: 'bool' is a keyword with '-std=c23' onwards
setup.h:4:1: warning: useless type name in empty declaration
    4 | typedef int bool;
      | ^~~~~~~
```

```
file.c:670:7: error: conflicting types for 'msg_href'; have 'char *(struct emailinfo *, struct emailinfo *, _Bool)'
  670 | char *msg_href(struct emailinfo *to_email, struct emailinfo *from_email, bool generate_markup)
      |       ^~~~~~~~
In file included from hypermail.h:426,
                 from file.c:27:
proto.h:48:7: note: previous declaration of 'msg_href' with type 'char *(struct emailinfo *, struct emailinfo *, int)'
   48 | char *msg_href(struct emailinfo *, struct emailinfo *, int);
      |       ^~~~~~~~
```
2025-07-31 01:11:58 +00:00
..