engine: Korean and Telex let Escape through after committing

A pending Hangul syllable is real text, and Escape is what vi users
press to leave insert mode; eating it and dropping the syllable served
nobody.  fcitx5-hangul commits and passes any key it does not consume,
Escape included; do the same for Korean and Telex.  A Japanese reading
is still cancelled: there Escape is the IME's own key.

strans.c

@@ -704,7 +704,7 @@ transition(u32int ks, u32int mod, Str *com)
 			flush(com);
 		return 1;
 	}
-	if(ks == Ktab || ks == Kret){
+	if(ks == Ktab || ks == Kret || (ks == Kesc && !isjp(&im))){
 		if(!haspre(&im))
 			return 0;
 		flush(com);