Resolve ERR_MISSING_GLUE / ERR_EXTRA_AAAA value collision

Both constants were defined as 5. The symbol table used by checkns() to
deduplicate log messages keys on (name, error_code), so logging an
extra-AAAA error caused logged() to also return true for the
missing-glue check, silently skipping the entire missing-glue block for
the same name in named-checkzone and named-checkconf -z.

Convert the ERR_* defines to an auto-numbered enum so the compiler
guarantees the values stay pairwise distinct.

Assisted-by: Claude:claude-opus-4-7
(cherry picked from commit 72d21a0806)

bin/check/check-tool.c

@@ -58,14 +58,16 @@
 #define CHECK_LOCAL 1
 #endif /* ifndef CHECK_LOCAL */
 
-#define ERR_IS_CNAME	   1
-#define ERR_NO_ADDRESSES   2
-#define ERR_LOOKUP_FAILURE 3
-#define ERR_EXTRA_A	   4
-#define ERR_EXTRA_AAAA	   5
-#define ERR_MISSING_GLUE   5
-#define ERR_IS_MXCNAME	   6
-#define ERR_IS_SRVCNAME	   7
+enum {
+	ERR_IS_CNAME = 1,
+	ERR_NO_ADDRESSES,
+	ERR_LOOKUP_FAILURE,
+	ERR_EXTRA_A,
+	ERR_EXTRA_AAAA,
+	ERR_MISSING_GLUE,
+	ERR_IS_MXCNAME,
+	ERR_IS_SRVCNAME,
+};
 
 static const char *dbtype[] = { "rbt" };