configure.ac: add explanation for max numbers properties

configure.ac

@@ -2429,7 +2429,10 @@ AC_MSG_NOTICE([
 
 	Compile-time limits
 	(change these with --enable-maxcpus, --enable-maxcudadev,
-	--enable-maxopencldev, --enable-maxbuffers)
+	--enable-maxopencldev, --enable-maxmicdev, --enable-maxnodes,
+        --enable-maxbuffers)
+        (Note these numbers do not represent the number of detected
+	devices, but the maximum number of devices StarPU can manage)
 
 	Maximum number of CPUs:           $maxcpus
 	Maximum number of CUDA devices:   $nmaxcudadev