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)
diff --git a/src/version.c b/src/version.c
index 862b3d9..8ae3dda 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1923,
+/**/
     1922,
 /**/
     1921,