Fix GH-19570: unable to fseek in /dev/zero and /dev/null

[nielsdos]

On Linux, these two character devices are exceptions in that they can be seeked. Check their major/minor device number.

[devnexen]

note that not just linux, allows some character devices being seekable, e.g. freebsd and very likely macos. The equivalent for freebsd at least, can t rely on device versions at all but on a "poorer" solution such as if fseek returns -1 and errno is ESPIPE then it is not seekable.

[divinity76]

/dev/mem and /dev/kmem and /dev/port are also seekable.
actually seems there are a lot of seekable character devices.
How about

#ifdef __linux__
    if (S_ISCHR(self->sb.st_mode)) {
        if (major(self->sb.st_rdev) == 1) {
            unsigned m = minor(self->sb.st_rdev);
            self->is_seekable =
                m == 1 ||   /* /dev/mem   */
                m == 2 ||   /* /dev/kmem  */
                m == 3 ||   /* /dev/null  */
                m == 4 ||   /* /dev/port  (seekable, offset = I/O port) */
                m == 5 ||   /* /dev/zero  */
                m == 7;     /* /dev/full  */
        } else {
            self->is_seekable = false;
        }
    } else {
        self->is_seekable = !S_ISFIFO(self->sb.st_mode);
    }
#else