More WHOWAS parameters

Adds parameters to the WHOWAS command.  Both are optional.
1. The `count` parameter, which is specified in the RFC but apparently isn't widely supported (I had a small sample size, though.  At least one other IRCd supports it.)  Specifies the number of results to receive (up to the maximum).
2. An oper-only parameter to show the host as something else (current options are "realhost" and "ip" which basically show what you expect: "ip" shows the IP address, and "realhost" shows their resolved host even if their host was cloaked or they had a vhost at the time of recording).  (This is from your request.)  (This is also unique to txircd.)

When specifying both parameters, the count must go first.  Invalid parameters (beyond the nick which is required) are simply ignored.
Data saved in old versions will have the realhost populated with the saved host, and the IP will be 0.0.0.0.  Entries populated after the upgrade will have the appropriate information filled in correctly.