dump: Recognize "fd:" protocols on Windows hosts

A few QMP command can work with named file descriptors.

The only way to create a named file descriptor used to be QMP command
getfd, which only works on POSIX hosts.  Thus, named file descriptors
were actually usable only there.

They became usable on Windows hosts when we added QMP command
get-win32-socket (commit 4cda177c601 "qmp: add 'get-win32-socket'").

Except in dump-guest-memory, because qmp_dump_guest_memory() compiles
its named file descriptor code only #if !defined(WIN32).

Compile it unconditionally, like we do for the other commands
supporting them.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20231031104531.3169721-4-armbru@redhat.com>

dump/dump.c

@@ -2170,14 +2170,12 @@ void qmp_dump_guest_memory(bool paging, const char *protocol,
         return;
     }
 
-#if !defined(WIN32)
     if (strstart(protocol, "fd:", &p)) {
         fd = monitor_get_fd(monitor_cur(), p, errp);
         if (fd == -1) {
             return;
         }
     }
-#endif
 
     if  (strstart(protocol, "file:", &p)) {
         fd = qemu_open_old(p, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR);