Support non-unicode flag

[Timmmm]

It would be cool to support the regex::bytes::Regex matcher using the non-unicode flag. If I try this regex:

(?-u).

I get the following error:

Syntax(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
regex parse error:
    (?-u).
         ^
error: pattern can match invalid UTF-8
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
)

In fact you may just want to use the regex::bytes::Regex unconditionally.