Extban support

[vanosg]

Patch by: Geo

One-line summary:
Add extban support

Additional description (if needed):
This PR does the following:

• Adds the '.+extban' command which adds the ability to insert an extban flag to a ban. This is essentially a wrapper for the .+ban command. This was allegedly done for backwards compatibility, but maybe it's not needed?

• Stores the EXTBAN 005 flags

• Stores the ACCOUNTEXTBAN 005 flag

• Removes the previous banmask "fixing" that was preventing Eggdrop from creating extban-formatted banmasks. These banmaks are now able to be stored in the banlist just like a normal ban.

• Handles extbans in two ways- enforceable, and non-enforceable

• • Enforceable extbans are modes Eggdrop can enforce with a kick based on things like account, realname, etc. These bans are treated like normal bans in the banlist and are subject to all the same rules (ie, dynamic bans, ban-time, etc)
• • • Enforceable bans should be activated in the normal ways- when a matching ban is placed, when a matching user joins, etc
• • • Currently supports only ACCOUNTEXTBAN flag and the U flag.
• • Non-enforceable bans are modes that Eggdrop can't enforce and are instead closer to server modes than bans (things like blocking a user from sending notices, ctcps, etc). These bans are treated like sticky bans.
• • • Currently supports the following non-enforceable modes obtained from https://defs.ircdocs.horse/defs/extbans.html: p, q, Q, A, B, c, N, and T

• Any extban flag can be used create and store an internal ban in Eggdrop, but Eggdrop will only activate an extban on channel if the server allows that flag to be created (ie, stored in EXTBAN 005 flag)

TO DOs:

Add in long-form extban flags ('account' instead of 'a', etc)
Add in more enforceable flags