xdiff: fix a hard crash on Windows The xdiff case of test-diff-antipatience.t started crashing in the C extension with 882657a9f768 (with 6a71a5ba666b backported so it compiles). There are a few more instances of 'long', but this resolves the crashing.

templater: split template functions to new module It has grown enough to be a dedicated module.

templater: move hybrid class and functions to templateutil module And make _hybrid and _mappable classes public. _showlist() is still marked as private since it's weird and third-party codes shouldn't depend on it.

templater: move stringify() to templateutil module As we have a util module, it doesn't make sense to import stringify() from templatefilters.py.