Fix missing std::tr1::hash on GCC 4.1

[matthauck]

Rather than crashing on use (doh!) better to just declare this platform
is missing a proper hash_map/hash_set implementation and use
the std::map/std::set emulation.

Fixes regression introduced by #1913

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[bazel-io]

Can one of the admins verify this patch?

[xfxyjwf]

Closing as this seems a duplicate of #2906

[matthauck]

Yes, this was an intentional duplicate (see comment on #1913). I wasn't sure which implementation would be preferred.

[xfxyjwf]

I see. I actually prefer the fallback to approach in this PR. The other PR casts int64 to size_t for hash and that is too week a hash function that invites hash flooding for 32bit systems where size_t is only 32bit.

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[bazel-io]

Can one of the admins verify this patch?

[xfxyjwf]

ok to test

[matthauck]

looks like there are conflicts here now. 😢

[bazel-io]

Can one of the admins verify this patch?

[matthauck]

ok. updated with master. Is there anything left pending on this PR to pull this in?

[matthauck]

ping.