Sagemaker-training

* bug-fix: Rename libchangehostname to gethostname to match POSIX function name

* feature: C extension reads hostname from resourceconfig instead of env var.

* feature: Generic OpenMPI support
* bug-fix: Fix response content_type handling

* bug-fix: Accept header ANY ('*/*') fallback to default accept
* feature: Add intermediate output to S3 during training
* bug-fix: reintroduce ``_modules.s3_download`` and ``_modules.download_and_install`` for backward compatibility

* feature: add capture_error flag to process.check_error and process.create and to all functions that runs process: modules.run, modules.run_module, and entry_point.run

* bug-fix: reintroduce _modules.prepare to import_module