ibus: die where startup fails; print the Plan 9 way; drop what said nothing

ibusinit unwound its server and un-registered its atexit handler on a
failure whose only sequel was ibusthread dying anyway; now each failure
dies with its own message, and the test that existed to walk that
unwind goes with it.  Also gone: an empty watch-toggle callback where
libdbus takes nil, Maxconns as a second name for Maxclients, fprintf
and strerror where the rest of the daemon says fprint and %r, USED()
where a parameter can simply be unnamed, a second findcontext() for the
Properties branch, and emitcommit() taking a connection and path apart
from the context that has both.  Ownerpoll lives once, in dat.h.

xim/xim.c

@@ -32,11 +32,6 @@ struct Ic
 	Caret		caret;
 };
 
-enum
-{
-	Ownerpoll = 200,	/* ms between owner checks while a preedit shows */
-};
-
 static xcb_connection_t *conn;
 static xcb_im_t *xim;
 static struct xkb_state *kstate;