Incorrect assignment to uppercase hex literals

[ynaffitgnay]

Overview

A variable is assigned the incorrect value when there are uppercase letters in the literal. An example to reproduce the problem can be found at https://github.com/ynaffitgnay/CascadeBenches/blob/master/bugreports/uppercase_hex_assignment.v

The current output is:

>>> ffffffffffffffed
>>> deaddeaddeaddead

It should be:

>>> deaddeaddeaddead
>>> deaddeaddeaddead