do away with symbols.template in windows

If the one provided in the zip/distribution is newer, replace
the one used by the game after renaming the current one to
symbols.save.

If the one used by the game is newer, do nothing with it.

sys/windows/Makefile.mingw32

@@ -772,7 +772,7 @@ CLEAN_FILE += $(NHTARGET) $(NHOBJS) $(NHRES)
 all: install
 
 TO_INSTALL = $(GAMEDIR)/NetHack.exe $(RTARGETS) \
-	     $(addprefix $(GAMEDIR)/, $(addsuffix .template, sysconf symbols .nethackrc) \
+	     $(addprefix $(GAMEDIR)/, $(addsuffix .template, sysconf .nethackrc) \
 	     Guidebook.txt NetHack.txt license opthelp record)
 
 ifeq "$(USE_LUADLL)" "Y"
@@ -798,7 +798,7 @@ ifneq "$(USE_DLB)" "Y"
 endif
 	@echo NetHack is up to date.
 
-$(GAMEDIR)/symbols.template: $(DAT)/symbols
+$(GAMEDIR)/symbols: $(DAT)/symbols
 	cp $< $@
 
 $(GAMEDIR)/NetHack.txt: $(DOC)/nethack.txt