gcc warning with current cvs

[Peter Bloomfield <PeterBloomfield MindSpring com>]

>  send.c: In function `libbalsa_message_postpone':
>  send.c:1151: warning: `thereturn' might be used uninitialized in 
>this function

The code has a tacit assumption that either 
LIBBALSA_IS_MAILBOX_LOCAL(draftbox) or 
LIBBALSA_IS_MAILBOX_IMAP(draftbox), and `thereturn' would be used 
uninitialized if both of these fail. We should probably either assert 
that one or the other is true, or add a catch-all `else thereturn = 
-1;' -- don't know which is preferred.

Peter