arrow

ARROW-3451: [C++/Python] pyarrow and numba CUDA interop

This PR implements the following features:
1. `pyarrow.cuda.Context.handle` property returns `CUcontext` value
2. `pyarrow.cuda.Context.from_numba` method to create `Context` that shares numba context handler
3. `pyarrow.cuda.Context.to_numba` method to create a numba context instance that shares `Context` handler
4. `pyarrow.cuda.foreign_buffer` method to create CudaBuffer of device memory defined by address and size. Resolved ARROW-3451.
5. `pyarrow.cuda.CudaBuffer.to_numba` method to create a numba `MemoryPointer` instance so that `CudaBuffer` memory is used within the arguments to numba jitted functions.
6. `pyarrow.cuda.CudaBuffer.from_numba` method to create a CudaBuffer view of device data represented by numba `MemoryPointer`.
7. `CudaDeviceManager::CreateSharedContext` used in 2. Resolves ARROW-1423.
8. `CudaContext::View` used in 4.

Author: Pearu Peterson <pearu.peterson@gmail.com>
Author: Kouhei Sutou <kou@clear-code.com>
Author: Antoine Pitrou <pitrou@free.fr>
Author: Pindikura Ravindra <ravindra@dremio.com>

Closes #2732 from pearu/arrow-cuda and squashes the following commits:

b503b0ca <Antoine Pitrou> Update docstring for GetContext
b6f4ede2 <Pearu Peterson> Remove contexts_ cache and related methods CreateNewContext and CreateSharedContext.
8457e006 <Pearu Peterson> Use C++ style cast.
fc5f5058 <Pearu Peterson> Expose CudaContext device number for CudaBufferWriter in buffering mode.
39d3f69f <Pearu Peterson> Introduce CloseIpcBuffer, fixes IPC test.
767df424 <Pearu Peterson> Introduce device argument to AllocateHost. Use sync in IPC test.
3e99126e <Pearu Peterson> Implemented context push-pop pattern. 2nd try.
1b0c19ee <Pearu Peterson> Implemented context push-pop pattern.
f9e69b2c <Pearu Peterson> Fix check-format issues.
415cbd6e <Pearu Peterson> Introduce synchronize methods.
c546ce51 <Pearu Peterson> Synchronize before copying device data to host.
cfb1e74a <Pearu Peterson> Fix lint issue.
a6d53765 <Pearu Peterson> Introduce ContextSaver. Fix doc strings. Set fixed seed for cuda tests.
cc87f3b4 <Pearu Peterson> Fix lint issues.
f27796a1 <Pearu Peterson> Restore previous context after cuCtxSetCurrent. Remove use_numba_context.
c1b57177 <Pearu Peterson> Fix bug that enabled using numba context manager always.
42fc2324 <Pearu Peterson> Fix make lint failures.
bdc00cee <Pearu Peterson> Introduce GetSharedContext and use_numba_context.
f5764747 <Pearu Peterson> Fix compiler warning re casting pointers with different sizes.
1bf7856c <Pearu Peterson> Moved numba jitted function inside the test function.
740e4747 <Pearu Peterson> Apply feedback from pitrou
cbe73382 <Pearu Peterson> Fix lint-clang formatting issues.
0920105a <Pearu Peterson> lost it git messages
14789098 <Pearu Peterson> Implement a view of device memory (CudaBuffer.foreign_buffer)
1107aade <Pearu Peterson> pyarrow and numba CUDA interop
3a1e5645 <Pearu Peterson> Fix lint issues.
a42ffd1a <Pearu Peterson> Merge branch 'arrow-cuda' of github.com:Quansight/arrow into arrow-cuda
ef69f35a <Pearu Peterson> Implement interop between pyarrow and numba.
cba9bcf5 <Pearu Peterson> Merging with upstream/master
50aebe65 <Pearu Peterson> Implement interop between pyarrow and numba.
4e20aa9e <Kouhei Sutou> ARROW-3438:  Fix too much Markdown escape in CHANGELOG
5284ad07 <Pindikura Ravindra> ARROW-3331:  Add re2 to toolchain
cf3aebe6 <Kouhei Sutou> ARROW-3432:  Expand variables in commit message
b6294015 <Kouhei Sutou> ARROW-3431:  Include Gemfile to archive
f16148f4 <Kouhei Sutou> ARROW-3430:  Add workaround to verify 0.11.0