engine: look dictionaries up synchronously

The dictionary thread ran in imthread's own proc, so a lookup could
only start once the engine blocked, and it was a trie probe anyway; the
emoji and Hanja searches already called dictlookup directly. The
request/result channels, sequence numbers, staleness checks and the
second draw per Japanese key are gone; dictqjp fills the candidates
in place. Emit.dict and Lang.dictq only ever triggered lookups for
Vietnamese, which has no dictionary. dictlookup(Lang*, key, out, max)
returns the count. The Hanja lookup no longer pre-checks for a single
syllable; a reading either has an entry or it does not.

dat.h

@@ -54,7 +54,6 @@ struct Emit
 	int	eat;
 	Str	s;
 	Str	next;
-	Str	dict;
 };
 
 typedef struct Tnode Tnode;
@@ -91,7 +90,6 @@ struct Lang
 	char	*dictname;
 	Emit	(*trans)(Im*, Rune);
 	void	(*back)(Im*);
-	void	(*dictq)(Im*);
 	Trie	*map;
 	Trie	*dict;
 };
@@ -190,28 +188,7 @@ struct Keyreq
 	Channel	*reply;
 };
 
-typedef struct Dictreq Dictreq;
-struct Dictreq
-{
-	Str	key;
-	Str	pre;
-	int	lang;
-	u32int	seq;
-};
-
-typedef struct Dictres Dictres;
-struct Dictres
-{
-	Str	key;
-	Str	kouho[Maxkouho];
-	int	nkouho;
-	int	lang;
-	u32int	seq;
-};
-
 extern Lang langs[];
 extern int nlang;
 extern Channel *drawc;
 extern Channel *keyc;
-extern Channel *dictreqc;
-extern Channel *dictresc;