Convert many RGL modules from Latin-1 to UTF-8 to speed up compilation

Also add flags coding=utf8 to silence warnings.

src/chinese/ConstructionChi.gf

@@ -2,6 +2,7 @@
 
 concrete ConstructionChi of Construction = CatChi ** 
   open SyntaxChi, ParadigmsChi, (L = LexiconChi), (E = ExtraChi), (G = GrammarChi), (R = ResChi), Prelude in {
+flags coding=utf8 ;
 
 
 lin

src/chinese/QuestionChi.gf

@@ -2,6 +2,7 @@ concrete QuestionChi of Question = CatChi **
   open ResChi, Prelude in {
 
   flags optimize=all_subs ;
+  flags coding=utf8 ;
 
   lin