Fully-strict version of Data.IntMap.Strict

Unlike Data.IntMap.Strict IntMap which is an alias to Data.IntMap.Lazy IntMap, the instances of our {- haddock #1251 -} IntMap are all strict as well.

You should be able to switch from the former simply by changing your module imports, and your package dependency from containers to strict-containers. If this doesn't work, please file a bug.

The documentation in the auto-generated modules have not been updated in a particularly sophisticated way, so may sound weird or contradictory. In those cases, please re-interpret such weird wording in the context of the above.