The exceprt-include macro cannot find exceprt macros put inside other macros

[raphj]

If an excerpt macro is not at the root of a document, but inside a macro, excerpt-include won't find it because we don't recursively look for it:

https://github.com/xwikisas/xwiki-pro-macros/pull/210/files#diff-4cbedb6b2d35d5d474de7982f2907c87f27a2690e1b2d91164c388ba84baaf86R115-R116

(thanks for spotting this @michitux)