The white and yellow stuff would be what makes our own urine yellow in tint, and while you may never have noticed it your snake does excrete quite a bit of fluid when urinating, this will soak into whatever bedding you may have making it stink to high heaven, and that is from the ammonia. If you have shaving based bedding (aspen, cypress, etc) then you want to remove the bedding around said chunks of white and yellow, because the ammonia is actually fairly bad for your snake. If you use things like mats or sheets of newspaper then you will want to change that weekly.

As for the poo, just wait until your snake becomes constipated. When it hasn't pooped in 3 months and the feces is the same width as your snake and about an eighth of it's body length.