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.

strans.c

@@ -3,7 +3,7 @@
 
 static Im im;
 static void *activeowner;
-static int activecap;
+static int clientpre;	/* the owner draws its own preedit */
 static Caret caret;
 static Drawcmd lastdraw;
 static Emit transjp(Im*, Rune);
@@ -191,7 +191,7 @@ snapshot(Drawcmd *dc)
 		pre = search.text;
 	else
 		impre(&im, &pre);
-	if(!(activecap & Cclientpreedit))
+	if(!clientpre)
 		dc->pre = pre;
 	if(search.lang && pre.n == 0)	/* a search just begun shows itself */
 		sputr(&dc->pre, search.lang == LangEMOJI ? L'☺' : L'漢');
@@ -881,7 +881,7 @@ init(void)
 	memset(&search, 0, sizeof search);
 	memset(&caret, 0, sizeof caret);
 	activeowner = nil;
-	activecap = 0;
+	clientpre = 0;
 	memset(&lastdraw, 0, sizeof lastdraw);
 }
 
@@ -905,7 +905,7 @@ imhandlekey(Keyreq *kr)
 		if(kr->owner == activeowner){
 			flush(&res.commit);
 			activeowner = nil;
-			activecap = 0;
+			clientpre = 0;
 		}
 		break;
 	case Keyreset:
@@ -919,17 +919,17 @@ imhandlekey(Keyreq *kr)
 	case Keycap:
 		res.eaten = kr->owner == activeowner;
 		if(res.eaten)
-			activecap = kr->cap & Cclientpreedit;
+			clientpre = kr->clientpre;
 		break;
 	case Keypress:
 		res.eaten = 0;
 		if(kr->owner == activeowner)
-			activecap = kr->cap & Cclientpreedit;
+			clientpre = kr->clientpre;
 		if(keymeaningful(kr->ks)){
 			if(kr->owner != activeowner){
 				reset();
 				activeowner = kr->owner;
-				activecap = kr->cap & Cclientpreedit;
+				clientpre = kr->clientpre;
 			}
 			caret = kr->caret;
 			res.eaten = transition(kr->ks, kr->mod, &res.commit);