redefine the default shared_constructor fct to be float32_shared_constructor for cuda.

theano/sandbox/cuda/__init__.py

@@ -98,6 +98,7 @@ if cuda_available:
             CudaNdarrayConstant,
             CudaNdarraySharedVariable,
             float32_shared_constructor)
+    shared_constructor = float32_shared_constructor
 
     import basic_ops
     from basic_ops import (GpuFromHost, HostFromGpu, GpuElemwise,