Revert "ARROW-85 memcmp can be avoided in Equal when comparing with the same Buffer"
Revert "ARROW-85 memcmp can be avoided in Equal when comparing with the same Buffer"

This reverts commit dbc37ddebe2df56204d917d2c4436f01c396db21.

drankye/arrow,drankye/arrow,drankye/arrow,drankye/arrow,drankye/arrow,drankye/arrow