Closes #9596
Consistency is king. Following the lead in everything curl. Closes #8159
This makes the tests easier to copy and relocate to other test numbers without having to update content. Closes #6738
curl_mime_encoder() is operational and documented. curl tool -F option is extended with ";encoder=". curl tool --libcurl option generates calls to curl_mime_encoder(). New encoder tests 648 & 649. Test 1404 extended with an encoder specification.
