Issue #882: Optimize iteration over iterables whose static type is a Tuple.
Issue #882: Tests for the optimization of iteration over iterables whose static type is a Tuple.
Issue #882: Fix a nasty bug in the ArraySequence iteration optimization.
Issue #882: Improved test for the static ArraySequence iteration optimization by ensuring that the iterated ArraySequence doesn't have a trivial backing array. This exposed the nasty bug fixed in the previous commit.

Also update .src changed by that fix.