tests: test IMAP, POP3 and SMTP over HTTP proxy tunnel

tests/data/test1321

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+<testcase>
+<info>
+<keywords>
+IMAP
+FETCH
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+From: me@somewhere
+To: fake@nowhere
+
+body
+
+--
+  yours sincerely
+</data>
+<datacheck>
+HTTP/1.1 200 Mighty fine indeed
+
+From: me@somewhere
+To: fake@nowhere
+
+body
+
+--
+  yours sincerely
+</datacheck>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+imap
+http-proxy
+</server>
+ <name>
+IMAP FETCH tunneled through HTTP proxy
+ </name>
+ <command>
+imap://%HOSTIP:%IMAPPORT/1321 -u user:secret -p -x %HOSTIP:%PROXYPORT
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+B LOGIN user secret
+C SELECT 1321
+D FETCH 1 BODY[TEXT]
+A LOGOUT
+</protocol>
+<proxy>
+CONNECT %HOSTIP:%IMAPPORT HTTP/1.1
+Host: %HOSTIP:%IMAPPORT
+User-Agent: curl/7.24.0-DEV (i686-pc-linux-gnu) libcurl/7.24.0-DEV OpenSSL/1.0.0e zlib/1.2.3.4 c-ares/1.7.6-DEV libidn/1.23 libssh2/1.4.0_DEV librtmp/2.2e
+Proxy-Connection: Keep-Alive
+
+</proxy>
+</verify>
+</testcase>