engine: the Korean keyboard's 한/영 and 한자 keys

A Korean keyboard sends Hangul and Hangul_Hanja for its two extra keys;
they did nothing but end the composition.  Now 한/영 toggles Korean and
English and 한자 opens the Hanja search, by standing in for Ctrl+S,
Ctrl+T, and Ctrl+H, as fcitx5-hangul binds them.

strans.c

@@ -682,6 +682,14 @@ transition(u32int ks, u32int mod, Str *com)
 		ks = kokey(ks, mod);
 	else if(isjp(&im) && ks >= 'A' && ks <= 'Z')
 		ks += 'a' - 'A';	/* romaji is case-blind, Caps Lock included */
+	/* The Korean keyboard's 한/영 and 한자 keys are Ctrl+S or Ctrl+T, and Ctrl+H. */
+	if(ks == Khangul){
+		ks = im.l->lang == LangKO ? 't' : 's';
+		mod = Mctrl;
+	}else if(ks == Khanja){
+		ks = 'h';
+		mod = Mctrl;
+	}
 	if(search.lang)
 		return searchkey(ks, mod, com);
 	n = movedelta(ks);