Introduce support for CUDA streams
Need to downcast exec with derived_cast before calling stream().
Use cudaMemcpyAsync inside trivial_copy's implementation. For now, all host <-> device copies happen on stream 0
Add simple_cuda_streams example.
Eliminate superfluous <iostream>
Avoid identifiers with leading underscores.
Bump subminor version number.
Avoid deriving from std::unary_function & std::binary_function.
Eliminate unused variable warning in CUDA's reduce_by_key
implementation.
Add CHANGELOG for 1.7.1

Fixes #421
Merge branch 'master' of github.com:jaredhoberock/thrust into streams
Launch radix sort kernels on the execution policy's stream
Merge branch 'master' of github.com:jaredhoberock/thrust into streams
Compile in 64bit, and remove 64 suffix from library on OSX. Fixes #356
Remove commented out code.
Initial complex implementation, ported from cusp
Improve complex exp, log and norm
Files that implemented the improved functions
Split float/double function in two files
Organize better the detail::complex functions