patch 8.1.0610: MS-Windows ctags file list differs from Unix

Problem:    MS-Windows ctags file list differs from Unix.
Solution:   Define TAGS_FILES in the common makefile. (partly by Ken Takata)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index a35708d..5e22470 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -1270,8 +1270,7 @@
 
 
 tags: notags
-	$(CTAGS) *.c *.cpp *.h
-	if exist auto\if_perl.c $(CTAGS) --append=yes auto\if_perl.c
+	$(CTAGS) $(TAGS_FILES)
 
 notags:
 	- if exist tags del tags