add new version of Windows documentation that use pythonxy to have a simpler installation. Their is test instruction for the gpu on windows.

make GpuFromHost return a dtype of the same dtype as the input. As CudaNdarray support only float32, an error will be raised.

fix MakeVector.make_node to upcast its input correctly. fix stack to don't downcast float* to int64 and to don't upcast inputs more then necessary.

MakeVector.make_node upcast the input to the dtype received in __init__, but don't allow to loose precission.

fix a bug in optimization of two consecutive sum. Add a warning when we hit this case. The warning can be disabled by the theano flags warn.sum_sum_bug=False.