ARROW-3209: [C++] Rename libarrow_gpu to libarrow_cuda

[pitrou]

Also rename the arrow::gpu namespace to arrow::cuda.

[pitrou]

I think the C glib side needs to be fixed, but I'm not sure how. @kou would you like to push something to this PR?

[wesm]

Ah, I forgot about the disruption that this would cause to the glib side, where there are also Linux packages. I think it's a good idea to leave open the possibility of GPU computing outside of CUDA

[kou]

I'll add some commits for C GLib, Ruby and Linux packages to this PR.

[kou]

It seems that Cuda in arrow::cuda::Cuda* is redundant.
Should we keep Cuda or remove Cuda?

[codecov-io]

Codecov Report

Merging #3088 into master will increase coverage by 1.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3088      +/-   ##
==========================================
+ Coverage   87.12%   88.15%   +1.03%     
==========================================
  Files         492      434      -58     
  Lines       69104    65339    -3765     
==========================================
- Hits        60204    57601    -2603     
+ Misses       8801     7738    -1063     
+ Partials       99        0      -99

Impacted Files	Coverage Δ
cpp/src/plasma/client.cc	84.68% <ø> (ø)	⬆️
cpp/src/plasma/protocol.cc	95.62% <ø> (ø)	⬆️
cpp/src/plasma/plasma.h	100% <ø> (ø)	⬆️
cpp/src/plasma/store.h	100% <ø> (ø)	⬆️
cpp/src/plasma/store.cc	92.42% <ø> (ø)	⬆️
cpp/src/plasma/common.h	100% <ø> (ø)	⬆️
cpp/src/plasma/test/client_tests.cc	100% <ø> (ø)	⬆️
go/arrow/array/table.go
go/arrow/math/uint64_amd64.go
go/arrow/internal/testing/tools/bool.go
... and 55 more

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[pitrou]

It seems that Cuda in arrow::cuda::Cuda* is redundant. Should we keep Cuda or remove Cuda?

I'd keep it.

[kou]

OK.
+1 from me.

We can merge this when Linux packages are built on Travis CI:
https://github.com/kou/crossbow/branches/all?utf8=%E2%9C%93&query=build-53

[wesm]

Some of the Linux packages failed

[kou]

Linux package builds are fixed: https://github.com/kou/crossbow/branches/all?utf8=%E2%9C%93&query=build-54

I'll merge this when CI is passed.

[wesm]

Great, thanks @kou!

[kou]

CI is green. I'll merge this.