PersonIdent: Strip some special chars from external strings

PersonIdent: Strip some special chars from external strings

The special characters <> and '\n' interfere with parsing of
identities. C git strips these special characters, so we should too.

Rather than allocating extra strings by calling String#trim(), add a
few lines to our sanitization method to perform the same trimming as
described in String's Javadoc.

Change-Id: I96edcb93a2fc194ee354d60566d352299742a52f