Clear conversation window from a protocol prpl

[avictor.za at gmail.com]

hi Paul,

> Unfortunately, this constitutes an API change, and would need to wait
> for 2.8.0.

Isn't that the reason for the "purple_reserved" entries in struct
_PurpleConversationUiOps?
ie, some optional methods can be added without increasing
sizeof(PurpleConversationUiOps), so a re-compile of external plugins
would not be required?  It's an API "extension", rather than an API
"change".


Regards,
  Andrew Victor