Better self-contained examples

The array flip examples weren't very good - the first lacked an output (as well as a purpose?) and the second was confusing as it reused variables and used strange variable names.

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Provided by James Ward (james@notjam.es)

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@335231 c90b9560-bf6c-de11-be94-00142212c4b1
Remove information about "track_vars" setting, which was apparently removed in PHP 4.0.3. Quite how the description came to mention superglobals, which only appeared in 4.1, I don't know.

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Provided by Rowan Collins (rowan.collins@gmail.com)

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@335232 c90b9560-bf6c-de11-be94-00142212c4b1