content_encoding: Transfer-Encoding parser improvements

- allow and ignore "identity" as an encoding

- fail if any other encoder than chunked follows after chunked

- fail on unsolicited encodings - when the server encodes but curl did
  not ask for it

Add test 1493 to 1496 to verify.

Disable test 319 as that is now broken: issue #16974

Reported-by: Jonathan Rosa
Fixes #16956
Closes #16959

tests/data/test319

@@ -3,8 +3,8 @@
 <keywords>
 HTTP
 HTTP GET
-compressed
 Transfer-Encoding
+--raw
 </keywords>
 </info>
 #
@@ -15,7 +15,7 @@ HTTP/1.1 200 OK swsclose
 Date: Mon, 29 Nov 2004 21:56:53 GMT
 Server: Apache/1.3.31 (Debian GNU/Linux) mod_gzip/1.3.26.1a PHP/4.3.9-1 mod_ssl/2.8.20 OpenSSL/0.9.7d mod_perl/1.29
 Content-Type: text/html; charset=ISO-8859-1
-Transfer-Encoding: gzip
+Transfer-Encoding: gobbledigook
 Content-Length: 44
 
 %hex[%1f%8b%08%08%79%9e%ab%41%00%03%6c%61%6c%61%6c%61%00%cb%c9%cc%4b%55%30%e4%52%c8%01%d1%46%5c]hex%
@@ -34,14 +34,11 @@ Content-Length: 44
 #
 # Client-side
 <client>
-<features>
-libz
-</features>
 <server>
 http
 </server>
 <name>
-HTTP GET gzip transfer-encoded data in raw mode
+HTTP GET gobbledigook transfer-encoded data in raw mode
 </name>
  <command option="no-include">
 http://%HOSTIP:%HTTPPORT/%TESTNUMBER --raw