Update INSTALL about no-md5 removal

no-rsa is no longer an option since 7ec8de16

Fix a typo about poly1305

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1582)
(cherry picked from commit e2562bbb)