patch 8.1.1923: some source files are not in a normal encoding

Problem:    Some source files are not in a normal encoding.
Solution:   Convert hangulin.c from euc-kr to utf-8 and digraph.c from latin1
            to utf-8. (Daniel Hahler, closes #4731)

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1923,
 /**/
     1922,
 /**/