Remove support for FreeBSD prior to 7.0 from the Handbook.

More specifically:

• mentions of old versions of FreeBSD in historical context are left in tact
• remove section about KerberosIV
• remove section about SAP R/3
• remove mentions of XFree86
• only support gvinum
• update examples to 7.X or 8.X
• remove Alpha support
• add COMPAT_FREEBSD[67] kernel options
• csup(1) now only in the base system
• update (tty) device names, add warnings for 7.X
• remove MD5 from the port checksum algorithms
• update port versions (probably not all)
• add definitions for ctm-src[5-8] to mailing-lists.ent

Reviewed by: bcr, joel, remko, simon