patch 8.1.0825: code for autocommands is mixed with file I/O code

Problem:    Code for autocommands is mixed with file I/O code.
Solution:   Move autocommand code to a separate file. (Yegappan Lakshmanan,
            closes #3863)
diff --git a/src/Make_ivc.mak b/src/Make_ivc.mak
index 784cab9..0459984 100644
--- a/src/Make_ivc.mak
+++ b/src/Make_ivc.mak
@@ -211,6 +211,7 @@
 LINK32_OBJS= \
 	$(EXTRAS) \
 	"$(INTDIR)/arabic.obj" \
+	"$(INTDIR)/autocmd.obj" \
 	"$(INTDIR)/blowfish.obj" \
 	"$(INTDIR)/buffer.obj" \
 	"$(INTDIR)/charset.obj" \
@@ -341,6 +342,10 @@
 SOURCE=.\arabic.c
 # End Source File
 # Begin Source File
+#
+SOURCE=.\autocmd.c
+# End Source File
+# Begin Source File
 
 SOURCE=.\blowfish.c
 # End Source File