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).

win/win32/mhmain.c

@@ -5,6 +5,7 @@
 
 #include "winMS.h"
 #include <commdlg.h>
+#include "date.h"
 #include "patchlevel.h"
 #include "resource.h"
 #include "mhmsg.h"
@@ -986,7 +987,8 @@ LRESULT CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
 							NH_A2W(
 								COPYRIGHT_BANNER_A "\n"
 								COPYRIGHT_BANNER_B "\n"
-								COPYRIGHT_BANNER_C,
+								COPYRIGHT_BANNER_C "\n"
+								COPYRIGHT_BANNER_D,
 								wbuf,
 								BUFSZ
 							) );