Correct outdated object size limit

The comment here about 48 bit addresses being enough was written in 2016 but was made incorrect in 2019 by 5-level paging, and then persisted for another 5 years before being noticed and corrected.

The bolding of the "exclusive" part is merely to call attention to something I missed when reading it and doublechecking the math.

try-job: i686-msvc
try-job: test-various

rustc_expand: remember module `#[path]`s during expansion

During invocation collection, if a module item parsed from a `#[path]` attribute needed a second pass after parsing, its path wouldn't get added to the file path stack, so cycle detection broke. This checks the `#[path]` in such cases, so that it gets added appropriately. I think it should work identically to the case for external modules that don't need a second pass, but I'm not 100% sure.

Fixes #97589