urlapi: provide more detailed return codes

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