XHR Event aren't protected by o2cl() method

Some events (o_ffXHREvent) aren't protected by the o2cl() method and doesn't trigger the spinner. This behavior is needed in calendar for a better integration to the third party javascript library but the page size selector and the header sort of the flexitable need to trigger the spinner if needed. The following events must be changed:

• Page size selector of flexible
• Header sort in flexitable
• Standard link in flexitable
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