patch 9.0.0421: MS-Windows makefiles are inconsistently named

Problem:    MS-Windows makefiles are inconsistently named.
Solution:   Use consistent names. (Ken Takata, closes #11088)
diff --git a/src/GvimExt/Makefile b/src/GvimExt/Makefile
index 4b83f52..18b91ec 100644
--- a/src/GvimExt/Makefile
+++ b/src/GvimExt/Makefile
@@ -1,98 +1,4 @@
-# Makefile for GvimExt, using MSVC
-# Options:
-#   DEBUG=yes		Build debug version (for VC7 and maybe later)
-#   CPUARG=		/arch:IA32/AVX/etc, call from main makefile to set
-#   			automatically from CPUNR
-#
+!message This makefile is deprecated. Use Make_mvc.mak instead.
+!message
 
-TARGETOS = WINNT
-
-!ifndef APPVER
-APPVER = 5.01
-!endif
-!ifndef WINVER
-WINVER = 0x0501
-!endif
-
-!if "$(DEBUG)" != "yes"
-NODEBUG = 1
-!endif
-
-!ifdef PROCESSOR_ARCHITECTURE
-# On Windows NT
-! ifndef CPU
-CPU = i386
-!  if !defined(PLATFORM) && defined(TARGET_CPU)
-PLATFORM = $(TARGET_CPU)
-!  endif
-!  ifdef PLATFORM
-!   if ("$(PLATFORM)" == "x64") || ("$(PLATFORM)" == "X64")
-CPU = AMD64
-!   elseif ("$(PLATFORM)" == "arm64") || ("$(PLATFORM)" == "ARM64")
-CPU = ARM64
-!   elseif ("$(PLATFORM)" != "x86") && ("$(PLATFORM)" != "X86")
-!    error *** ERROR Unknown target platform "$(PLATFORM)". Make aborted.
-!   endif
-!  endif
-! endif
-!else
-CPU = i386
-!endif
-
-!ifdef SDK_INCLUDE_DIR
-!include $(SDK_INCLUDE_DIR)\Win32.mak
-!elseif "$(USE_WIN32MAK)"=="yes"
-!include <Win32.mak>
-!else
-cc = cl
-link = link
-rc = rc
-cflags = -nologo -c
-lflags = -incremental:no -nologo
-rcflags = /r
-olelibsdll = ole32.lib uuid.lib oleaut32.lib user32.lib gdi32.lib advapi32.lib
-!endif
-
-# include CPUARG
-cflags = $(cflags) $(CPUARG)
-
-# set WINVER and _WIN32_WINNT
-cflags = $(cflags) -DWINVER=$(WINVER) -D_WIN32_WINNT=$(WINVER)
-
-!if "$(CL)" == "/D_USING_V110_SDK71_"
-rcflags = $(rcflags) /D_USING_V110_SDK71_
-!endif
-
-SUBSYSTEM = console
-!if "$(SUBSYSTEM_VER)" != ""
-SUBSYSTEM = $(SUBSYSTEM),$(SUBSYSTEM_VER)
-!endif
-
-!if "$(CPU)" == "AMD64" || "$(CPU)" == "ARM64"
-OFFSET = 0x11C000000
-!else
-OFFSET = 0x1C000000
-!endif
-
-all: gvimext.dll
-
-gvimext.dll:    gvimext.obj	\
-		gvimext.res
-	$(link) $(lflags) -dll -def:gvimext.def -base:$(OFFSET) -out:$*.dll $** $(olelibsdll) shell32.lib comctl32.lib -subsystem:$(SUBSYSTEM)
-	if exist $*.dll.manifest mt -nologo -manifest $*.dll.manifest -outputresource:$*.dll;2
-
-gvimext.obj: gvimext.h
-
-.cpp.obj:
-	$(cc) $(cflags) -DFEAT_GETTEXT $(cvarsmt) $*.cpp
-
-gvimext.res: gvimext.rc
-	$(rc) /nologo $(rcflags) $(rcvars)  gvimext.rc
-
-clean:
-	- if exist gvimext.dll del gvimext.dll
-	- if exist gvimext.lib del gvimext.lib
-	- if exist gvimext.exp del gvimext.exp
-	- if exist gvimext.obj del gvimext.obj
-	- if exist gvimext.res del gvimext.res
-	- if exist gvimext.dll.manifest del gvimext.dll.manifest
+!include Make_mvc.mak