PHP: add support for "<script language=php>" open and close tags

http://www.php.net/manual/en/language.basic-syntax.phptags.php
PHP: recognize PHP 5.5 keywords finally and yield as such
PHP: Fix infinite loop reading an identifier ending at EOF

Bit-wise operation is inappropriate here because `c` might be negative,
since EOF is generally represented as -1.  Since -1 is stored as all
bits at 1 on most common architectures, the test will evaluate to true,
hence entering an infinite loop.