ipc: strip machinery no peer uses; keep client state in one Keyreq

ipc.c: an AF_UNIX nonblocking connect completes at once or fails with
EAGAIN, so the EINPROGRESS/poll/SO_ERROR path and the fcntl juggling
were dead; the deadline plumbing checked a clock that cannot fail and
re-tested the deadline before every transfer although only waitfd
blocks; readfield's truncation and discard loop served the unit test,
since every caller owns char[Ipcfieldmax+1]; NULL-argument checks on
in-tree encoders are gone (peer validation stays). The primary key frame
is Ipckey, not 'legacy'; ipckeysym names the keysym mapping.

srv.c: the per-connection capability and caret already lived in the
persistent Keyreq; the mirror locals and 'negotiated' flag guarded a
protocol rule no client relied on. proccreate never fails in libthread.

gtk: focus-out no longer round-trips a reset before closing the socket
that releases the engine; the caret dedup compares the packed frame;
srvconnect's preedit no-ops and the insimple flag are gone.

xim/xim.c

@@ -555,7 +555,7 @@ kpress(Ic *state, xcb_key_press_event_t *ev)
 	int n, wasvalid;
 
 	key = keymaplookup(kstate, ev->detail, ev->state);
-	key = ipckey(key, xkb_keysym_to_utf32(key));
+	key = ipckeysym(key, xkb_keysym_to_utf32(key));
 	if(meaningful(key)){
 		wasvalid = state->caret.valid;
 		refreshplace(state);