DCOM-243 Added check for Zend OPcache extenstion

[victorsmirnov]

Please check the original issue http://www.doctrine-project.org/jira/browse/DCOM-243
I think the fix might be as simple as this.

[stof]

actually, it is the previous check which should be fixed. Using opcache was introduced before the name was settled in PHP and it has not been updated when the final name Zend OPcache was chosen

[victorsmirnov]

I don't mind ;)
We might have both checks.

[stof]

well, the opcache extension does not exist (except in some dev versions of PHP before the 5.5 release)

[victorsmirnov]

Christophe, I did not know this. Then let's just fix the name.