Updated the list of PHP reserved keywords

Source: http://php.net/manual/en/reserved.keywords.php
bug #314 Updated the list of PHP reserved keywords (javiereguiluz)

This PR was merged into the 2.4.x-dev branch.

Discussion
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Updated the list of PHP reserved keywords

We didn't consider the keywords introduced in 5.4 and 5.5 versions.

Source: http://php.net/manual/en/reserved.keywords.php

Commits
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035fc8f Updated the list of PHP reserved keywords