Merge copy_survey() and copySurveySession()

[ywarnier]

In main/survey/survey.lib.php, copy_survey() and copySurveySession() do practically the same things (with a difference of 2 parameters which are only used once).

Merge those 2 functions into one with a bit more options.

[christianbeeznest]

It is fixed with this commit 9d2eb0a

Thanks for confirmation.

[ywarnier]

As far as I can tell, this works.