patch 8.0.1252: incomplete translations makefile for MinGW/Cygwin

Problem:    Incomplete translations makefile for MinGW/Cygwin.
Solution:   Add missing source files.  Make it work with msys2's bash. (Ken
            Takata)
diff --git a/src/po/Make_cyg.mak b/src/po/Make_cyg.mak
index 4a86d28..f8e45ba 100644
--- a/src/po/Make_cyg.mak
+++ b/src/po/Make_cyg.mak
@@ -128,11 +128,11 @@
 
 first_time:
 	$(XGETTEXT) --default-domain=$(LANGUAGE) \
-		--add-comments --keyword=_ --keyword=N_ $(wildcard ../*.c) ../if_perl.xs $(wildcard ../globals.h)
+		--add-comments --keyword=_ --keyword=N_ $(wildcard ../*.c) ../if_perl.xs ../GvimExt/gvimext.cpp $(wildcard ../globals.h) ../if_py_both.h
 
 $(LANGUAGES):
 	$(XGETTEXT) --default-domain=$(PACKAGE) \
-		--add-comments --keyword=_ --keyword=N_ $(wildcard ../*.c) ../if_perl.xs $(wildcard ../globals.h)
+		--add-comments --keyword=_ --keyword=N_ $(wildcard ../*.c) ../if_perl.xs ../GvimExt/gvimext.cpp $(wildcard ../globals.h) ../if_py_both.h
 	$(MV) $(PACKAGE).po $(PACKAGE).pot
 	$(CP) $@.po $@.po.orig
 	$(MV) $@.po $@.po.old