engine: the Japanese keyboard's own keys; keypad arrows move through candidates

半角/全角, ひらがな/カタカナ, 変換, and 無変換 committed the reading and did
nothing, like any function key.  They now stand for what a Japanese
keyboard means by them: toggling Japanese and English, switching kana
modes, converting (or turning Japanese on), and turning it off; the
Korean keys became a switch of the same shape.  The keypad's arrows
and page keys, with NumLock off, fold onto the plain ones as its Enter
and Tab already did.

ipc.c

@@ -166,7 +166,8 @@ ipcconnect(void)
 /*
  * Engine key for an X keysym and its Unicode value: printable characters
  * as themselves, the function keysyms 0xff00-0xffff as Kspec+offset.
- * The keypad and Shift+Tab (ISO_Left_Tab) variants fold onto Enter and Tab.
+ * The keypad keys and Shift+Tab (ISO_Left_Tab) fold onto their plain
+ * counterparts.
  */
 uint32_t
 ipckeysym(uint32_t sym, uint32_t unicode)
@@ -179,6 +180,14 @@ ipckeysym(uint32_t sym, uint32_t unicode)
 		return Ktab;
 	case 0xff8d:
 		return Kret;
+	case 0xff97:
+		return Kup;
+	case 0xff99:
+		return Kdown;
+	case 0xff9a:
+		return Kpgup;
+	case 0xff9b:
+		return Kpgdown;
 	}
 	if(sym >= 0xff00 && sym <= 0xffff)
 		return Kspec + (sym - 0xff00);