2017-03-23 Daniel Kruegler <daniel.kruegler@gmail.com>
Implement LWG 2686, Why is std::hash specialized for error_code,
but not error_condition?
* include/std/system_error (hash<error_condition>): Define for C++17.
* testsuite/20_util/hash/operators/size_t.cc (hash<error_condition>):
Instantiate test for error_condition.
* testsuite/20_util/hash/requirements/explicit_instantiation.cc
(hash<error_condition>): Instantiate hash<error_condition>.
From-SVN: r246424
