switch afp test to Darwin on macbroy2

--- a/Admin/isatest/settings/afp-poly	Wed Jan 18 10:05:23 2012 +0100
+++ b/Admin/isatest/settings/afp-poly	Wed Jan 18 22:09:29 2012 +1100
@@ -3,8 +3,8 @@
 CONTRIB=~/afp/contrib
 
   POLYML_HOME=$CONTRIB/polyml
-  ML_SYSTEM="polyml-5.4.0"
-  ML_PLATFORM="x86_64-linux"
+  ML_SYSTEM="polyml-5.4.1"
+  ML_PLATFORM="x86-darwin"
   ML_HOME="$POLYML_HOME/$ML_PLATFORM"
   ML_OPTIONS="-H 2000 --gcthreads 4"