patch 8.0.1178: using old compiler on MS-Windows

Problem:    Using old compiler on MS-Windows.
Solution:   Switch default build on MS-Windows to use MSVC 2015. (Ken Takata)
diff --git a/src/xxd/Make_mvc.mak b/src/xxd/Make_mvc.mak
index 3227f0c..0133d73 100644
--- a/src/xxd/Make_mvc.mak
+++ b/src/xxd/Make_mvc.mak
@@ -1,14 +1,19 @@
 # The most simplistic Makefile for Win32 using Microsoft Visual C++
 # (NT and Windows 95)
 
+SUBSYSTEM = console
+!if "$(SUBSYSTEM_VER)" != ""
+SUBSYSTEM = $(SUBSYSTEM),$(SUBSYSTEM_VER)
+!endif
+
 xxd: xxd.exe
 
 xxd.exe: xxd.c
-     cl /nologo -DWIN32 xxd.c
+	cl /nologo -DWIN32 xxd.c -link -subsystem:$(SUBSYSTEM)
 
 # This was for an older compiler
 #    cl /nologo -DWIN32 xxd.c /link setargv.obj
 
 clean:
-     - if exist xxd.obj del xxd.obj
-     - if exist xxd.exe del xxd.exe
+	- if exist xxd.obj del xxd.obj
+	- if exist xxd.exe del xxd.exe