patch 8.2.0443: clipboard code is spread out

Problem:    Clipboard code is spread out.
Solution:   Move clipboard code to its own file. (Yegappan Lakshmanan,
            closes #5827)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index 99c004f..c51225b 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -710,6 +710,7 @@
 	$(OUTDIR)/change.o \
 	$(OUTDIR)/charset.o \
 	$(OUTDIR)/cindent.o \
+	$(OUTDIR)/clipboard.o \
 	$(OUTDIR)/cmdexpand.o \
 	$(OUTDIR)/cmdhist.o \
 	$(OUTDIR)/crypt.o \