Fix bug in 0x20 encoding.

We must only compare case when mapping an answer from upstream
to a forwarding record, not when checking a query to see if it's a
duplicate. Since the saved query name is scrambled, that ensures
that almost all such checks will wrongly fail.

Thanks to Peter Tirsek for an exemplary bug report for this.

src/dnsmasq.h

@@ -775,6 +775,7 @@ struct dyndir {
 #define FREC_DO_QUESTION       64
 #define FREC_HAS_PHEADER      128
 #define FREC_GONE_TO_TCP      256
+#define FREC_ANSWER           512
 
 struct frec {
   struct frec_src {