Convert (most of) the test data files into genuine XML. A handful still

are not, due mainly to the lack of support for XML character entities
(e.g. & => & ).  This will make it easier to validate test files using
tools like xmllint, as well as edit and view them using XML tools.

tests/data/test15

@@ -1,3 +1,4 @@
+<testcase>
 <info>
 <keywords>
 HTTP
@@ -7,7 +8,7 @@ HTTP GET
 </info>
 # Server-side
 <reply>
-<data nocheck=true>
+<data nocheck="true">
 HTTP/1.4 200 OK
 Fake: yes
 Fake: yes
@@ -53,3 +54,4 @@ Accept: */*
 
 </protocol>
 </verify>
+</testcase>