match 'return-path' header case-insensitively, according to RFC2822
match 'return-path' header case-insensitively, according to RFC2822

git-svn-id: e9fe9b84e32fc5e57b7d09c40cd78b14ea28ed71@158666 13f79535-47bb-0310-9956-ffa450edef68

apache/spamassassin,apache/spamassassin,apache/spamassassin,apache/spamassassin,apache/spamassassin