Semi colon is not treated as RDN separator

[shaiacs]

A DN may contain RDNs that are separated by semi colons. Looks like the current code doesn't handle this correctly.
I believe this can be fixed by changing the following lines in Dn.parseDn method:
Line 104 from:
case char == ',' || char == '+':
to:
case char == ',' || char == '+' || char == ';':

Line 112 from:
if char == ',' {
to:
if char == ',' || char == ';' {

[cpuschma]

From rfc2253:

4. Relationship with RFC 1779 and LDAPv2
   [...]
   Implementations MUST allow a semicolon character to be used instead
   of a comma to separate RDNs in a distinguished name, and MUST also
   allow whitespace characters to be present on either side of the comma
   or semicolon. The whitespace characters are ignored, and the
   semicolon replaced with a comma.

I'll look into this week and propose a PR