Don't pass -m64 if address-model is 32_64 (or anything != 64).

[SVN r57061]

src/tools/gcc.jam

@@ -373,10 +373,12 @@ rule setup-address-model ( targets * : sources * : properties * )
             {
                 option = -m32 ;
             }
-            else
+            else if $(model) = 64
             {
                 option = -m64 ;
             }
+            # For darwin, the model can be 32_64. darwin.jam will handle that
+            # on its own.
         }
         OPTIONS on $(targets) += $(option) ;
     }