Addition of calendar to intl

Hi I have exposed ICU's Calendar API to PHP via the intl extension. It allows date calculations with Gregorian, Chinese, Coptic, Ethiopic, Hebrew, Indian, Islamic (civil/religious), Japanese, Persian, Taiwan and Thai Buddhist calendars. For a broader overview of its functionality, see: http://icu-project.org/apiref/icu4c/classCalendar.html I have committed already this change: https://github.com/php/php-src/commit/1c16c89b96bb4e02850b198b901feebdb8da2269 Traditionally, these kinds of additions to the intl extension (that mostly exposed 1 to 1 the ICU API) have not been preceded (or even followed) by any discussion; however, Stas expressed the opinion this is not a proper course of action nowadays. Consequently, if anyone has any non-trivial substantive (as opposed to procedural) concern with this change, I will revert the merge and submit an RFC. -- Gustavo Lopes