The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
LLVM always prints IR constants as signed decimal, which is not ideal when looking for packed bit patterns in tests. Add a little filter script that turns hex constants of the form `<iNN 0xNNNNN>` into the decimal output we'd expect from the LLVM printer.