LWG 2145 - mark constructor for std::error_category as inline and constexpr. Leave the (existing, out-of-line, non-constexpr) in the dylib for compatibility with existing programs)


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@188858 91177308-0d34-0410-b5e6-96231b3b80d8