fix: retain the active owner's caret

dat.h

@@ -118,12 +118,23 @@ struct Im
 };
 
 typedef struct Drawcmd Drawcmd;
+typedef struct Caret Caret;
+struct Caret
+{
+	int	valid;
+	int	x;
+	int	y;
+	int	w;
+	int	h;
+};
+
 struct Drawcmd
 {
 	Str	pre;
 	Str	kouho[Maxdisp];
 	int	nkouho;
 	int	sel;
+	Caret	caret;
 };
 
 typedef struct Keyreq Keyreq;
@@ -133,6 +144,7 @@ enum
 	Keypress,
 	Keyreset,
 	Keyrelease,
+	Keycaret,
 };
 struct Keyres
 {
@@ -147,6 +159,7 @@ struct Keyreq
 	int	op;
 	u32int	ks;
 	u32int	mod;
+	Caret	caret;
 	int	want;	/* nonzero: include preedit in reply */
 	Channel	*reply;
 };