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.

fn.h

@@ -20,8 +20,7 @@ int	trielookup(Trie*, Str*, char**, int*);
 Lang*	getlang(int);
 void	langinit(char*);
 
-void	dictthread(void*);
-void	dictlookup(Dictreq*, Dictres*);
+int	dictlookup(Lang*, Str*, Str*, int);
 
 void	drawthread(void*);
 void	popuparea(Area*, int, Area*, int, int, Area*);