Dump compiler warnings to *.warnings.txt; use "make warn" to print them
Output a lint report for every source file linted; use to lint
incrementally
Merge pull request #649 from jeffdonahue/warnlog

"make warn" to print compilation warnings; "make lint" runs incrementally
Avoid using cudaMemcpy for memcpy when there is no GPU and CUDA driver
Check the GPU mode to decide which memcpy to use
Switch to GPU mode when pointer is move to or from GPU in SyncedMemory
Implement @Yangqing's solution to copy memory in the SyncedMemory