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_cyg_ming.mak b/src/Make_cyg_ming.mak
index e689bad..a54730b 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -730,6 +730,7 @@
 	$(OUTDIR)/getchar.o \
 	$(OUTDIR)/hardcopy.o \
 	$(OUTDIR)/hashtab.o \
+	$(OUTDIR)/highlight.o \
 	$(OUTDIR)/indent.o \
 	$(OUTDIR)/insexpand.o \
 	$(OUTDIR)/json.o \