Converts this value to its ASCII lower case equivalent in-place.
ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.
To return a new lowercased value without modifying the existing one,
use [`to_ascii_lowercase`].
[`to_ascii_lowercase`]: Self::to_ascii_lowercase
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
let mut uppercase_a = u8::from(b'A');
let lowercase_a = u8::from(b'a');
uppercase_a.make_ascii_lowercase();
assert_eq!(lowercase_a, uppercase_a);
# }
```