Amend 16a1aa99

Amend 16a1aa99

With the current settings, a theorem with several paragraphs will have several wrapper tags (i.e. two `<db:figure>`, with one paragraph each, one next to the other when it's the same theorem), while there should be only one (one `<db:figure>` with two paragraphs).

It makes me wonder whether DocBookWrapperMergeWithPrevious should be the default value. I don't see a case where it would be set to `false` with a wrapper tag, but the test suite isn't developed enough to make the change with peace of mind (i.e. remove the parameter `DocBookWrapperMergeWithPrevious` and consider it is always `true` in the code).

For the record, the current code also works with two subsequent theorems with two paragraphs each (see new test case).