Disable insecure SSL protocols at configure time

SSLv2 and SSLv3 have various protocol security flaws. They should
be disabled by default when configuring OpenSSL.

SSLv2 is known to be completely broken security-wise while for
SSLv3 there are high impact vulnerability security flaws known.

SSLv2:
  - https://en.wikipedia.org/wiki/Transport_Layer_Security#SSL_2.0
  - http://osvdb.org/56387

SSLv3:
- BEAST:
  - http://www.educatedguesswork.org/2011/09/security_impact_of_the_rizzodu.html
- Renegotiaton attack:
  - https://en.wikipedia.org/wiki/Transport_Layer_Security#Renegotiation_attack
  - http://www.g-sec.lu/practicaltls.pdf