Modify Dropout to allow backward pass in TEST phase

Conflicts:
	src/caffe/layers/dropout_layer.cpp
	src/caffe/layers/dropout_layer.cu
Fix var names in Dropout.cu
Added test to Dropout to check gradients during Test phase
Check that pointers are different before copying in caffe_copy and caffe_gpu_copy
Remove Cuda.major >= 2 check on Dropout test
Merge pull request #502 from sguada/fix_dropout_backward

Fix dropout backward in TEST phase