email-tests: Renamed the POP3 tests to be in the range 850-857

Started segregating the email protocol tests, into their own protocol
based ranges, in preparation of adding more e-mail related tests to the
test suite.

tests/data/test850

@@ -0,0 +1,48 @@
+<testcase>
+<info>
+<keywords>
+POP3
+RETR
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+From: me@somewhere
+To: fake@nowhere
+
+body
+
+--
+  yours sincerely
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+pop3
+</server>
+ <name>
+POP3 RETR
+ </name>
+ <command>
+pop3://%HOSTIP:%POP3PORT/800 -u user:secret
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+CAPA
+USER user
+PASS secret
+RETR 800
+QUIT
+</protocol>
+</verify>
+</testcase>