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ARROW-5292: [C++] Work around symbol visibility issues so building static libraries is not necessary when building unit tests on WIN32 platform

This was a bit gnarly to say the least but it addresses the issue.

This also includes my changes for ARROW-6457 which were needed to build with Visual Studio Community 2017

Closes #5283 from wesm/ARROW-5292 and squashes the following commits:

e879b6193 <Wes McKinney> Do not force Parquet static library build when unit tests are enabled
5454102f1 <Wes McKinney> Do not require static libraries for Parquet tools and examples
c6b325664 <Wes McKinney> Remove now non-existent schema_internal.cc
7ea1f40c1 <Wes McKinney> Export internal symbols to appease Windows
412b88504 <Wes McKinney> Fix clang warnings
e88b61775 <Wes McKinney> lint
b1dec3c04 <Wes McKinney> Add static helper library to use on WIN32 when building Parquet unit tests to get access to inaccessible symbols
6db9e928a <Wes McKinney> Try to add auxiliary static library on Windows so that we don't have to build all shared libraries

Authored-by: Wes McKinney <wesm+git@apache.org>
Signed-off-by: Wes McKinney <wesm+git@apache.org>