[C++] Use boost::filesystem for handling of platform-specific file path encodings

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Reporter: Wes McKinney / @wesm
Assignee: Max Risuhin / @maxhora

_{Note: This issue was originally created as ARROW-1339. Please see the migration documentation for further details.}

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Max Risuhin / @maxhora:
@wesm, it seems that boost::filesystem::path can be used to replace recently introduced PlatformFilename struct.
I have tried to use path::wstring and path::string, it seems it works fine.
I'm wondering if it was supposed here more changes than just replace PlatformFilename struct with boost::filesystem::path?

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Wes McKinney / @wesm:
I don't think so. The only complexity is getting the UTF8-encoded path so that console error messages displayed properly. But we have a unit test for this now, so it should be safe to refactor

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Wes McKinney / @wesm:
Issue resolved by pull request 964
#964