Nasty workaround for
http://bugs.gentoo.org/show_bug.cgi?id=287426

--- src/auths/call_radius.c
+++ src/auths/call_radius.c
@@ -10,6 +10,16 @@
 /* This file was originally supplied by Ian Kirk. The libradius support came
 from Alex Kiernan. */
 
+/* ugly hack to work around redefinition of ENV by radiusclient.h and
+ * db.h: define _DB_H_ so the db.h include thinks it's already included,
+ * we can get away with it like this, since this file doesn't use any db
+ * functions. */
+#ifndef _DB_H_
+#define _DB_H_ 1
+#define _DB_EXT_PROT_IN_ 1
+#define DB void
+#endif
+
 #include "../exim.h"
 
 /* This module contains functions that call the Radius authentication