Reduce the security bits for MD5 and SHA1 based signatures in TLS

Reduce the security bits for MD5 and SHA1 based signatures in TLS

This has as effect that SHA1 and MD5+SHA1 are no longer supported at
security level 1, and that TLS < 1.2 is no longer supported at the
default security level of 1, and that you need to set the security
level to 0 to use TLS < 1.2.

Reviewed-by: Tim Hudson <tjh@openssl.org>
GH: #10787