(var.h, plague.h): Since all that was left in var.h were some plague

defines, import these defines into plague.h, drop var.h and include
plague.h where appropriate.
Remove some 'register' keywords at the same time.
No functional changes.

include/plague.h

@@ -0,0 +1,41 @@
+/*
+ *  Empire - A multi-player, client/server Internet based war game.
+ *  Copyright (C) 1986-2004, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ *                           Ken Stevens, Steve McClure
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *  ---
+ *
+ *  See the "LEGAL", "LICENSE", "CREDITS" and "README" files for all the
+ *  related information and legal notices. It is expected that any future
+ *  projects/authors will amend these files as needed.
+ *
+ *  ---
+ *
+ *  plague.h: plague defines.
+ * 
+ */
+
+#ifndef _PLAGUE_H_
+#define _PLAGUE_H_
+
+#define	PLG_HEALTHY	0
+#define	PLG_DYING	1
+#define	PLG_INFECT	2
+#define	PLG_INCUBATE	3
+#define	PLG_EXPOSED	4
+
+#endif /* _PLAGUE_H_ */