Form date selectors should not offer far-future dates

When used in 32-bit systems, Moodle should not present the option to select dates beyond 2038, the Unix 32-bit time limit. The last year shown in the dropdown should be 2037.

We could do a PHP_INT_SIZE check but in fact I think this should probably be applied regardless of the system in use, because realistically nobody needs to set dates past 2037 anyway, and you'd get problems with backup/restore between 64 and 32 bit sites.

This was highlighted by issues around MDL-44070 but it turned out that these dates didn't work properly with the old system either.

(Note: Although the number of 32-bit Unix systems is decreasing, PHP on Windows is always affected by this restriction at present, even on 64-bit.)