patch 8.1.1693: syntax coloring and highlighting is in one big file

Problem:    Syntax coloring and highlighting is in one big file.
Solution:   Move the highlighting to a separate file. (Yegappan Lakshmanan,
            closes #4674)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 7ce8d3d..8901a7c 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -739,6 +739,7 @@
 	$(OUTDIR)\getchar.obj \
 	$(OUTDIR)\hardcopy.obj \
 	$(OUTDIR)\hashtab.obj \
+	$(OUTDIR)\highlight.obj \
 	$(OUTDIR)\indent.obj \
 	$(OUTDIR)\insexpand.obj \
 	$(OUTDIR)\json.obj \
@@ -1487,6 +1488,8 @@
 
 $(OUTDIR)/hashtab.obj:	$(OUTDIR) hashtab.c  $(INCL)
 
+$(OUTDIR)/highlight.obj:	$(OUTDIR) highlight.c  $(INCL)
+
 $(OUTDIR)/indent.obj:	$(OUTDIR) indent.c  $(INCL)
 
 $(OUTDIR)/insexpand.obj:	$(OUTDIR) insexpand.c  $(INCL)
@@ -1747,6 +1750,7 @@
 	proto/getchar.pro \
 	proto/hardcopy.pro \
 	proto/hashtab.pro \
+	proto/highlight.pro \
 	proto/indent.pro \
 	proto/insexpand.pro \
 	proto/json.pro \