ARROW-8000: [C++] Fix compilation on gcc 4.8
ARROW-8000: [C++] Fix compilation on gcc 4.8

It seems that `constexpr auto` with function pointers is not supported in gcc 4.8.

Closes #6538 from wesm/ARROW-8000-gcc48-fixes and squashes the following commits:

ca01694d7 <Wes McKinney> Fix compilation on gcc 4.8

Authored-by: Wes McKinney <3be70eed0275ec2606f002bff3514252e145d204@apache.org>
Signed-off-by: Sutou Kouhei <73218711cdd5d5c30ac66da3cc4d9d9204caf34b@clear-code.com>

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