Fix: Fails to parser when given string includes multibyte chars.
Fix: Fails to parser when given string includes multibyte chars.

Net::LDAP::Filter::FilterParser fails to parse when a given string
includes multibyte chars such as Japanese characters.
But this should support it according to RFC-2254.

This commit is to fix this failure.

cloudvolumes/ruby-net-ldap,javanthropus/ruby-net-ldap,javanthropus/ruby-net-ldap,bkeepers/ruby-net-ldap,cloudvolumes/ruby-net-ldap,astockwell/ruby-net-ldap,astockwell/ruby-net-ldap,bkeepers/ruby-net-ldap