Further improve my fixes to 1984/decot

When I restored the macros it allowed for reinstating the 'union'
instead of 'static struct' and it also allowed for reintroducing the 'x'
(which is '=') in that line so that it looks just like the original:

    union tag u x{4};

For documentation purposes this was added in the thanks file (in the
same part of that entry, the making it look more like the original which
is a worthy goal) as well.

1984/decot/decot.c

@@ -21,7 +21,7 @@ int dup, signal;
 	goto _0;
 
 _O: while (!(k['a'] <<= - dup)) {	/*/*\*/
-	static struct tag u = {4};
+	union tag u x{4};
   }
 }