Fix extraction of php strings

[mlocati]

Fix https://travis-ci.org/oscarotero/Gettext/jobs/110222372

[mlocati]

1. It's safer to replace the chars after having stripped out the encosing '
2. Let's use the PHP 5.3 way to define the arrays 😉
3. strtr is faster than str_replace
4. it's better to use strtr in this case, see the first answer of http://stackoverflow.com/questions/8177296/when-to-use-strtr-vs-str-replace )

[mlocati]

1. it's better to use strtr in this case, see the first answer of http://stackoverflow.com/questions/8177296/when-to-use-strtr-vs-str-replace )

A simpler example: https://3v4l.org/O5t0K

[oscarotero]

nice!