LDAP/LDIF UTF-8 friendly regexp

You can't require 'ldap/ldif' at all in ruby 2.0 due to an invalid multibyte range.

Possible alternatives: 

 - Use utf characters instead for the range (patch included)
 - Add a 'n' flag to the regexp to enforce US-ASCII
 - Don't use a range at all and use String.ascii_only?, though that would break 1.8 compatibility.