engine: the one capability is a flag

Cclientpreedit was a one-bit mask that every producer set as "want ?
Cclientpreedit : 0" and every consumer masked out again; nothing else
was ever going to join it.  Keyreq carries clientpre, an int that says
whether the client draws the preedit, and the engine and the XIM
context keep it under that name.

xim.c

@@ -16,7 +16,7 @@
 
 /*
  * One XIM input context.  Only PreeditCallbacks clients draw the preedit
- * themselves (cap); the popup shows it for the others.  engaged means the
+ * themselves (clientpre); the popup shows it for the others.  engaged means the
  * engine has seen a real key from this context and owes it a release.
  */
 typedef struct Ic Ic;
@@ -26,7 +26,7 @@ struct Ic
 	xcb_im_input_context_t	*xic;
 	xcb_im_client_t	*client;
 	int		engaged;
-	int		cap;
+	int		clientpre;
 	int		prestarted;
 	int		nprerune;
 	Caret		caret;
@@ -255,7 +255,7 @@ updatepreedit(Ic *state, Str *pre)
 	size_t nwire;
 	int i, nbyte;
 
-	if(!(state->cap & Cclientpreedit))
+	if(!state->clientpre)
 		return;
 	if(pre->n == 0){
 		clearpreedit(state);
@@ -291,7 +291,7 @@ sendrequest(Ic *state, int op, u32int key, u32int mod, Keyres *res)
 
 	memset(&kr, 0, sizeof kr);
 	kr.owner = state;
-	kr.cap = state->cap;
+	kr.clientpre = state->clientpre;
 	kr.op = op;
 	kr.ks = key;
 	kr.mod = ipcmod(mod);
@@ -471,7 +471,7 @@ iccreate(xcb_im_client_t *client, xcb_im_input_context_t *ic)
 	state->xic = ic;
 	state->client = client;
 	if(xcb_im_input_context_get_input_style(ic) & XCB_IM_PreeditCallbacks)
-		state->cap = Cclientpreedit;
+		state->clientpre = 1;
 	state->next = ics;
 	ics = state;
 	xcb_im_input_context_set_data(ic, state, icfree);