[RDY] Remove project-specific integer types: long_u. (2)

This is part of a series of PR's aimed at removing long_u from the codebase.
This PR deals with the following instances of long_u:

- Those within *eval* module.
- Those within *memfile* module.

It continues the work in #656, #757 towards fulfilling #459.
No. `got_int` continues to be `int` for the moment.
`FALSE` was changed to `false` because Clint insisting on it.
So, boolean `false` is being implicitly converted to int there. There are several like this, in the clint commit.

Regarding the `|=`, I personally like the short version most, but I'll change it if you want.