Change case of class names to match declarations

Found by running tests under a version of PHP patched to report
case mismatches as E_STRICT errors.

User classes:
* MIMEsearchPage
* MostlinkedTemplatesPage
* SpecialBookSources
* UnwatchedpagesPage

Internal classes:
* DOMXPath
* stdClass
* XMLReader

Did not change:
* testautoLoadedcamlCLASS
* testautoloadedserializedclass

Change-Id: Idc8caa82cd6adb7bab44b142af2b02e15f0a89ee