Tidy up CNAME representaion.

Use an explicit discriminator for the target union.

src/dnsmasq.h

@@ -289,7 +289,8 @@ union all_addr {
       struct crec *cache;
       char *name;
     } target;
-    unsigned int uid; /* 0 if union is char * */
+    unsigned int uid;
+    int is_name_ptr;  /* disciminates target union */
   } cname;
   struct {
     struct blockdata *keydata;
@@ -483,10 +484,6 @@ struct crec {
 
 #define UID_NONE      0
 /* Values of uid in crecs with F_CONFIG bit set. */
-/* cname to uid SRC_PTR are to locally-configured CNAME
-   so use UID_NONE for that to 
-   eliminate clashes with any other uid */
-#define SRC_PTR UID_NONE
 #define SRC_CONFIG    1
 #define SRC_HOSTS     2
 #define SRC_AH        3