rand v0.9.5: backport #1790 and #1791

[dhardy]

• Added a CHANGELOG.md entry

Summary

Backport #1790 to rand 0.9.5.

Motivation

This changes address an unsoundness issue: code like the following could yield a Distribution object yielding invalid char values when sampled (unsound):

        let json = r#"{"sampler":{"low":4294967200,"range":0,"thresh":0}}"#;
        let result = serde_json::from_str::<Uniform<char>>(json);