htsopt: fold HTS_TRAVEL_TEST_ALL into the hts_travel_scope enum

The -t "test all" flag was a stray #define sitting next to the scope
enum; make it an enum constant so the named travel values live in one
place. The mask (HTS_TRAVEL_SCOPE_MASK) stays a #define: it selects the
scope out of opt->travel, it is not a member of the value set.

Name and value (1 << 8) are unchanged, so every use site compiles
identically and opt->travel stays plain int. No ABI change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htsopt.h

@@ -342,17 +342,17 @@ typedef enum hts_seeker {
   HTS_SEEKER_UP = 1 << 1    /**< may ascend to parent directories */
 } hts_seeker;
 
-/* Link-following scope, stored in the low byte of opt->travel. */
+/* opt->travel: link-following scope in the low byte, flags OR'd in above it. */
 typedef enum hts_travel_scope {
   HTS_TRAVEL_SAME_ADDRESS = 0, /**< stay on the same address (host) */
   HTS_TRAVEL_SAME_DOMAIN = 1,  /**< stay on the same principal domain */
   HTS_TRAVEL_SAME_TLD = 2,     /**< stay on the same TLD (e.g. .com) */
-  HTS_TRAVEL_EVERYWHERE = 7    /**< follow links anywhere on the web */
+  HTS_TRAVEL_EVERYWHERE = 7,   /**< follow links anywhere on the web */
+  HTS_TRAVEL_TEST_ALL = 1 << 8 /**< also test forbidden URLs (-t) */
 } hts_travel_scope;
 
-/* Flags OR'd into opt->travel above the scope value. */
-#define HTS_TRAVEL_SCOPE_MASK 0xff   /**< mask selecting the scope value */
-#define HTS_TRAVEL_TEST_ALL (1 << 8) /**< also test forbidden URLs (-t) */
+/* Mask selecting the scope value out of opt->travel. */
+#define HTS_TRAVEL_SCOPE_MASK 0xff
 
 /* Text progress display detail (opt->verbosedisplay). */
 typedef enum hts_verbosedisplay {