display version and build info at startup (trunk only)

Tested on the unix port; I've updated as many other ports as I can figure
out but they're not tested.  See window.doc for info on the changed banner
lines.  Also adds the ability to override the generic "Unix" port - used now to get
"MacOSX" into the version line instead of "Unix" (so we don't scare people who don't
know what's going on).

sys/msdos/Makefile.BC

@@ -1629,7 +1629,7 @@ $(O)topl.B:     $(PCHB) $(WTTY)\topl.c     $(HACK_H) $(TERMCAP_H) $(WINTTY_H)
 	@echo $(BCOPTS2) $(CFLAGUB) >> $(VROOMMCFG)
 	$(CC) $(FLAGUB) $(COBJNAM)$@ $(WTTY)\topl.c
 
-$(O)wintty.o: $(PCHO) $(CONFIG_H) $(WTTY)\wintty.c $(PATCHLEVEL_H)
+$(O)wintty.o: $(PCHO) $(CONFIG_H) $(WTTY)\wintty.c $(PATCHLEVEL_H) $(DATE_H)
 	@type schema$(SCHEMA).bc | find "$(@B)_o" > $(VROOMMCFG)
 	@echo $(BCOPTS1) >> $(VROOMMCFG)
 	@echo $(BCOPTS2) $(CFLAGUO) >> $(VROOMMCFG)

sys/msdos/Makefile.GCC

@@ -1068,7 +1068,7 @@ $(O)termcap.o: ../win/tty/termcap.c $(HACK_H) $(INCL)/tcap.h
 $(O)topl.o: ../win/tty/topl.c $(HACK_H) $(INCL)/tcap.h
 	$(CC) $(cflags) -o$@ ../win/tty/topl.c
 $(O)wintty.o: ../win/tty/wintty.c $(HACK_H) $(INCL)/dlb.h \
-		$(PATCHLEV_H) $(INCL)/tcap.h
+		$(INCL)/date.h $(PATCHLEV_H) $(INCL)/tcap.h
 	$(CC) $(cflags) -o$@ ../win/tty/wintty.c
 $(O)Window.o: ../win/X11/Window.c $(INCL)/xwindowp.h $(INCL)/xwindow.h \
 		$(CONFIG_H)

sys/msdos/Makefile.MSC

@@ -988,7 +988,7 @@ termcap.o: $(WIN)\termcap.c $(HACK_H) $(INCL)\tcap.h
 topl.o: $(WIN)\topl.c $(HACK_H) $(INCL)\tcap.h
 	@$(CC) $(CFLAGS) $(SPECOPTS) /Fo$@ $(WIN)\topl.c
 wintty.o: $(WIN)\wintty.c $(HACK_H) $(INCL)\dlb.h \
-		$(INCL)\patchlev.h $(INCL)\tcap.h
+		$(INCL)\date.h $(INCL)\patchlev.h $(INCL)\tcap.h
 	@$(CC) $(CFLAGS) $(SPECOPTS) /Fo$@ $(WIN)\wintty.c
 
 # src dependencies