patch 8.2.0872: XIM code is mixed with multi-byte code

Problem:    XIM code is mixed with multi-byte code.
Solution:   Move the XIM code to a separate file. (Yegappan Lakshmanan,
            closes #6177)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index 4efc1d6..ce615b2 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -61,6 +61,7 @@
 	findfile.c						\
 	fold.c							\
 	getchar.c						\
+	gui_xim.c						\
 	hardcopy.c						\
 	hashtab.c						\
 	highlight.c						\