urlapi: provide more detailed return codes

Previously, the return code CURLUE_MALFORMED_INPUT was used for almost
30 different URL format violations. This made it hard for users to
understand why a particular URL was not acceptable. Since the API cannot
point out a specific position within the URL for the problem, this now
instead introduces a number of additional and more fine-grained error
codes to allow the API to return more exactly in what "part" or section
of the URL a problem was detected.

Also bug-fixes curl_url_get() with CURLUPART_ZONEID, which previously
returned CURLUE_OK even if no zoneid existed.

Test cases in 1560 have been adjusted and extended. Tests 1538 and 1559
have been updated.

Updated libcurl-errors.3 and curl_url_strerror() accordingly.

Closes #8049

include/curl/urlapi.h

@@ -48,6 +48,18 @@ typedef enum {
   CURLUE_NO_PORT,             /* 15 */
   CURLUE_NO_QUERY,            /* 16 */
   CURLUE_NO_FRAGMENT,         /* 17 */
+  CURLUE_NO_ZONEID,           /* 18 */
+  CURLUE_BAD_FILE_URL,        /* 19 */
+  CURLUE_BAD_FRAGMENT,        /* 20 */
+  CURLUE_BAD_HOSTNAME,        /* 21 */
+  CURLUE_BAD_IPV6,            /* 22 */
+  CURLUE_BAD_LOGIN,           /* 23 */
+  CURLUE_BAD_PASSWORD,        /* 24 */
+  CURLUE_BAD_PATH,            /* 25 */
+  CURLUE_BAD_QUERY,           /* 26 */
+  CURLUE_BAD_SCHEME,          /* 27 */
+  CURLUE_BAD_SLASHES,         /* 28 */
+  CURLUE_BAD_USER,            /* 29 */
   CURLUE_LAST
 } CURLUcode;