Add support for missing character classes

```scala
pass("\\h", " ")
pass("\\H", "a")
pass("\\v", "\n")
pass("\\V", "a")
pass("\\0100", "\u0040") // 100 octal = 40 hex
pass("\\xFF", "\u00FF")
pass("\\uBEEF", "\uBEEF")
pass("\\e", "\u001B") // escape
```