fix xml errors and build the stuff

$ build validate-xml
[xmlvalidate] .../manual/misc/perf-tuning.xml:139:45: The element type "section"
must be terminated by the matching end-tag "</section>".

(actually: missing <p>)

$build validate-xml
[xmlvalidate] .../manual/misc/perf-tuning.xml:477:12: Element type "i" must be de
clared.
[xmlvalidate] .../manual/misc/perf-tuning.xml:481:54: The content of element type
 "p" must match "(em|strong|code|a|br|directive|module|img|cite|q|dfn|var|transnote)".

(you meant <em>, put it there)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@98959 13f79535-47bb-0310-9956-ffa450edef68