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_cyg_ming.mak b/src/Make_cyg_ming.mak
index 79bff50..52156dd 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -983,11 +983,7 @@
 	$(MAKE) -C GvimExt -f Make_ming.mak CROSS=$(CROSS) CROSS_COMPILE=$(CROSS_COMPILE) CXX='$(CXX)' STATIC_STDCPLUS=$(STATIC_STDCPLUS)
 
 tags: notags
-	$(CTAGS) *.c *.cpp *.h
-ifdef PERL
-	$(CTAGS) --append=yes auto$(DIRSLASH)if_perl.c
-endif
-
+	$(CTAGS) $(TAGS_FILES)
 
 notags:
 	-$(DEL) tags