Message is unavailable functionality in TnyMsgViewIface implementations

[Philip Van Hoof <spam pvanhoof be>]

TnyMsgViewIface implementations now also have to implement the
set_unavailable method. The header parameter is optional (use NULL if
omitted). The method must show a message view (or another warning or
perform an action) where/if/when the message is unavailable.

In the applications being build using the API, this method can be used
to show the user that the message is unavailable. Its current implement-
ation simply shows "Message is unavailable" in a translatable string at
the location where otherwise the message body would be shown.

void (*set_unavailable_func) (TnyMsgViewIface *self, TnyMsgHeaderIface
*header);

The TnyMsgWindow TnyMsgViewIface implementation is also fixed. I forgot
to implement the set_save_strategy method. It now also implements this
new set_unavailable method. Both plus the method that was there already
decorate the TnyMsgViewIface instance which you passed at the construct-
or of the TnyMsgWindow type.


-- 
Philip Van Hoof, software developer at x-tend 
home: me at pvanhoof dot be 
gnome: pvanhoof at gnome dot org 
work: vanhoof at x-tend dot be 
http://www.pvanhoof.be - http://www.x-tend.be