sstephenson/prototype — pull request #88 by victor-homyakov (2012-12-27 10:38:23+00:00)
Title: Possibility to remove X-* headers for CORS request

`Ajax.Request#setRequestHeaders()` unconditionally adds specific headers to any request.

This patch gives possibility to remove these headers in order to allow simple CORS request.

Based on [Stack Overflow question](http://stackoverflow.com/questions/13814739/prototype-ajax-request-being-sent-as-options-rather-than-get-results-in-501-err) and [Ticket 1590](https://prototype.lighthouseapp.com/projects/8886/tickets/1590-ability-to-remove-headers-in-ajaxrequestsetrequestheaders-for-cors)