Remove sanity check for PHP 5.1.0- in date_i18n()

[SergeyBiryukov]

There's a sanity check for PHP 5.1.0- in date_i18n(), which doesn't allow dates before 1970 (for example, January 21, 1930).

The dates are perfectly stored in the database, however date_i18n() displays current date instead. Removing the check allows them to be displayed correctly. Since we are moving to PHP 5.2, the check is probably not needed any more.

[nacin]

#10332