* build: Bumped Go version to 1.10 [[GH-3988](https://github.com/hashicorp/consul/pull/3988)]
* agent: Blocking queries on service-specific health and catalog endpoints now return a per-service `X-Consul-Index` improving watch performance on very busy clusters. [[GH-3890](https://github.com/hashicorp/consul/issues/3890)]. **Note this may break blocking clients that relied on undocumented implementation details** as noted in the [upgrade docs](https://github.com/hashicorp/consul/blob/master/website/source/docs/upgrading.html.md#upgrade-from-version-106-to-higher).
* agent: Blocking queries on service-specific health and catalog endpoints now return a per-service `X-Consul-Index` improving watch performance on very busy clusters. [[GH-3890](https://github.com/hashicorp/consul/issues/3890)]. **Note this may break blocking clients that relied on undocumented implementation details** as noted in the [upgrade docs](https://github.com/hashicorp/consul/blob/main/website/source/docs/upgrading.html.md#upgrade-from-version-106-to-higher).
* agent: All endpoints now respond to OPTIONS requests. [[GH-3885](https://github.com/hashicorp/consul/issues/3885)]
* agent: List of supported TLS cipher suites updated to include newer options, [[GH-3962](https://github.com/hashicorp/consul/pull/3962)]
* agent: WAN federation can now be disabled by setting the serf WAN port to -1. [[GH-3984](https://github.com/hashicorp/consul/issues/3984)]