Replace tail recursion with while loop

[bartholinie]

Fixes #1087

[dnfclas]

All CLA requirements met.

[dnfclas]

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[quinmars]

Note, that #915 also removes the tail recursion.

[akarnokd]

I prefer #915 too. @quinmars Could you add the test from this PR to yours?

[quinmars]

I will do that this evening (CET). I hopefully can preserve the authorship with cherry picking.

[danielcweber]

Fixed by #915. Unit test from this PR made it there. Thank you for the effort.