patch 8.1.0857: indent functionality is not separated

Problem:    Ignore functionality is not separated.
Solution:   Move indent functionality into a new file. (Yegappan Lakshmanan,
            closes #3886)
diff --git a/src/Make_ivc.mak b/src/Make_ivc.mak
index 0459984..96d6a47 100644
--- a/src/Make_ivc.mak
+++ b/src/Make_ivc.mak
@@ -234,6 +234,7 @@
 	"$(INTDIR)/getchar.obj" \
 	"$(INTDIR)/hardcopy.obj" \
 	"$(INTDIR)/hashtab.obj" \
+	"$(INTDIR)/indent.obj" \
 	"$(INTDIR)/json.obj" \
 	"$(INTDIR)/list.obj" \
 	"$(INTDIR)/main.obj" \
@@ -434,6 +435,10 @@
 SOURCE=.\hashtab.c
 # End Source File
 # Begin Source File
+#
+SOURCE=.\indent.c
+# End Source File
+# Begin Source File
 
 SOURCE=.\gui.c