Test for im2col kernel

With associated Makefile changes for .cu tests

This tests that the grid-stride loop works for im2col,
using the CPU version as a reference.
Fix building tests with parallel make

The changes for .cu tests meant that creating
TEST_BUILD_DIR wasn't happening first
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
lint
Merge pull request #545 from jamt9000/im2col-kernel-test

Test for im2col kernel
Update Makefile.config.example

fix some typing error