src: add define of ENOMSG for MinGW

MinGW lacks ENOMSG until version 6.0.0 (Fedora 31).
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/internal.h

@@ -482,3 +482,9 @@ enum {
 #ifndef ENODATA
 # define ENODATA EIO
 #endif
+
+#ifdef WIN32
+# ifndef ENOMSG
+#  define ENOMSG 122
+# endif
+#endif