We want unsized literals to behave as if they have infinite size, so need to force them to be zero extended, even if the expression type is signed.
This patch is for devel only, and is based on the reworked expression elaboration code, so will not backport easily. v0.9 has a number of known issues with expression types and widths, so I'm inclined to leave well alone.
Also attached is a regression test for inclusion in the test suite. This doesn't need any special flags or a gold file.