Fix hash requirements check in __hash_table.

r296565 attempted to add better diagnostics when an unordered container
is instantiated with a hash that doesn't meet the Hash requirements.

However I mistakenly checked the wrong set of requirements. Specifically
it checked if the hash met the requirements for specializations of
std::hash. However these requirements are stricter than the generic
Hash requirements.

This patch fixes the assertions to only check the Hash requirements.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@296919 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed