(svn r1090) -Fix: Made the _openttd_revision variable global, and with that

hopefully killed the windows-revision problem. If WITH_REV is defined, 
for both Windows as *nix system _openttd_revision is filled with normal 
info, else _openttd_revision is set to 'norev000'
-Fix: Small possible server-crash

variables.h

@@ -426,6 +426,13 @@ VARDEF int _debug_grf_level;
 VARDEF int _debug_ai_level;
 VARDEF int _debug_net_level;
 
+/* Make the revision tag global */
+extern const char _openttd_revision[];
+#ifdef WITH_REV_HACK
+	/* Special rules for Windows */
+	#define WITH_REV
+#endif
+
 void CDECL debug(const char *s, ...);
 #ifdef NO_DEBUG_MESSAGES
 	#define DEBUG(name, level)