Check that email addresses do not contain <, >, or newline so they can
be quickly scanned without trouble.  The copy() function in ident.c
already ensures that ordinary git commands will not write email
addresses without this property.
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>