Use patched version of zend-locale

Use the patched version of `Zend_Locale_Format::convertPhpToIsoFormat`.
In order to use the `1.12.6` tag for all the zf1 components I added the `1.12.6` tag to my [patched fork](https://github.com/concrete5/concrete5-5.7.0/blob/d30668e70ee45763993d8abd03fc82c51493bd0e/web/concrete/composer.json#L5).