HTTP: add support for gzip and deflate Transfer-Encoding

Transfer-Encoding differs from Content-Encoding in a few subtle ways,
but primarily it concerns the transfer only and not the content so when
discovered to be compressed we know we have to uncompress it. There will
only arrive compressed transfers in a response after we have requested
them with the appropriate TE: header.

Test case 1122 and 1123 verify.

tests/data/test1122

@@ -0,0 +1,69 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+compressed
+Transfer-Encoding
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data base64="yes">
+SFRUUC8xLjEgMjAwIE9LDQpEYXRlOiBNb24sIDI5IE5vdiAyMDA0IDIxOjU2OjUzIEdNVA0KU2Vy
+dmVyOiBBcGFjaGUvMS4zLjMxIChEZWJpYW4gR05VL0xpbnV4KSBtb2RfZ3ppcC8xLjMuMjYuMWEg
+UEhQLzQuMy45LTEgbW9kX3NzbC8yLjguMjAgT3BlblNTTC8wLjkuN2QgbW9kX3BlcmwvMS4yOQ0K
+VmFyeTogQWNjZXB0LUVuY29kaW5nDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD1J
+U08tODg1OS0xDQpUcmFuc2Zlci1FbmNvZGluZzogZ3ppcA0KQ29udGVudC1MZW5ndGg6IDQ0DQoN
+Ch+LCAh5nqtBAANsYWxhbGEAy8nMS1Uw5FLIAdFGXAoQhjEXAAoCcWAYAAAA
+</data>
+
+<datacheck>
+HTTP/1.1 200 OK
+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
+Vary: Accept-Encoding
+Content-Type: text/html; charset=ISO-8859-1
+Transfer-Encoding: gzip
+Content-Length: 44
+
+line 1
+ line 2
+  line 3
+</datacheck>
+
+</reply>
+
+#
+# Client-side
+<client>
+<features>
+libz
+</features>
+<server>
+http
+</server>
+ <name>
+HTTP GET gzip transfer-encoded content
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/1122 -H "TE: gzip"
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+GET /1122 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+TE: gzip
+
+</protocol>
+</verify>
+</testcase>