[libstdc++-v3 parallel mode] lack of __gnu_parallel::copy and inconvenience of transform overload

[Bernard Hugueney]

While using __gnu_parallel, I could not guess nor find the reason not
to have a __gnu_parallel::copy, which should be embarrassingly
parallel for random iterators. I settled for __gnu_parallel::transform
using an identity Op, which brings me to my second question/remark :
given that the overload of std:transform (for 1 or 2 input sequences)
interferes with the additional optional parameter for __gnu_parallel::
algorithms, would it be possible to provide
__gnu_parallel::transform1(...,__gnu_parallel::_Parallelism ) and
__gnu_parallel::transform2(...,__gnu_parallel::_Parallelism ) to allow
an easy selection of the parallelism of the transform algorithms over
1 and 2 input sequences ?

Thanks,

Best regards,

Bernard