Insufficient regular expressions in checks

[ockham]

This:

<?php
/**/eval('echo "I am evil\n";');
;eval('echo "Me too\n";');
?>

isn't detected by ForbiddenPHPFunctionsCheck. The same regular expressions are also used in some other [Forbidden|Deprecated][Functions|Constants]Checks, so one could e.g. also do

$plugindir =PLUGINDIR;
echo $plugindir;

We need tests to cover this, and a proper tokenizer or parser instead of regular expressions.