[Patch] Fix wrong backup variable initialization in regex

[Paolo Carlini]

Forgot...

But in
>principle yes, since we deliver two, and the users have a way to choose
>
>which one they want (X) we should add to the testsuite 2 copies of each
>
>test which doesn't use br and test both executors.

In practice, of course, we could also avoid the 2 physical copies. For example via a very simple mechanism using a  macro.

I suppose it's up to you to decide if it's the right time for this kind of work or you prefer to concentrate on something else...

Paolo