Port forward from 2.4 branch:

Patch #1464708 from William McVey: fixed handling of nested comments in mail
addresses.  E.g.

"Foo ((Foo Bar)) <foo@example.com>"

Fixes for both rfc822.py and email package.  This patch needs to be back
ported to Python 2.3 for email 2.5.

Lib/email/_parseaddr.py

@@ -367,6 +367,7 @@ class AddrlistClass:
                 break
             elif allowcomments and self.field[self.pos] == '(':
                 slist.append(self.getcomment())
+                continue        # have already advanced pos from getcomment
             elif self.field[self.pos] == '\\':
                 quote = True
             else: