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_cyg_ming.mak b/src/Make_cyg_ming.mak
index d0b82f1..39f1e84 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -741,6 +741,7 @@
 	$(OUTDIR)/findfile.o \
 	$(OUTDIR)/fold.o \
 	$(OUTDIR)/getchar.o \
+	$(OUTDIR)/gui_xim.o \
 	$(OUTDIR)/hardcopy.o \
 	$(OUTDIR)/hashtab.o \
 	$(OUTDIR)/highlight.o \