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/Filelist b/Filelist
index 81a1553..73f842f 100644
--- a/Filelist
+++ b/Filelist
@@ -50,6 +50,7 @@
 		src/gui_beval.c \
 		src/hardcopy.c \
 		src/hashtab.c \
+		src/highlight.c \
 		src/indent.c \
 		src/insexpand.c \
 		src/json.c \
@@ -190,6 +191,7 @@
 		src/proto/gui_beval.pro \
 		src/proto/hardcopy.pro \
 		src/proto/hashtab.pro \
+		src/proto/highlight.pro \
 		src/proto/indent.pro \
 		src/proto/insexpand.pro \
 		src/proto/json.pro \