patch 8.1.0949: MS-windows defines GUI macros different than other systems

Problem:    MS-windows defines GUI macros different than other systems.
Solution:   Swap FEAT_GUI and FEAT_GUI_MSWIN. (Hirohito Higashi, closes #3996)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index 06bf07a..03953f4 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -491,7 +491,7 @@
 
 # See feature.h for a list of options.
 # Any other defines can be included here.
-DEF_GUI=-DFEAT_GUI -DFEAT_CLIPBOARD
+DEF_GUI=-DFEAT_GUI_MSWIN -DFEAT_CLIPBOARD
 DEFINES=-DWIN32 -DWINVER=$(WINVER) -D_WIN32_WINNT=$(WINVER) \
 	-DHAVE_PATHDEF -DFEAT_$(FEATURES) -DHAVE_STDINT_H
 ifeq ($(ARCH),x86-64)