Update DateFormat.php

In versions of PHP >= 5.5.0, the method IntlDateFormatter::setTimeZoneId() and IntlDateFormatter::setTimeZone() should be used instead.

This is my first proposed zf fix, so hopefully the ternary + dynamic method name var is acceptable.
Merge pull request #5295 from hickeroar/patch-1

Update DateFormat.php to fix deprecated method call: PHP >= 5.5.0.
[#5295] incorporate feedback

- Use more reliable version comparison
[#5295] consistent version checking

- use PHP_VERSION_ID always
- comparison should be against integers
Merge branch 'hotfix/5295'

Close #5295