Add Pending change PRs to change log.
Adds change PRs: to pending change log.
### SDK Features
### SDK Enhancements
+* `aws/credentials`: Add support for getting credential's ExpiresAt. ([#2375](https://github.com/aws/aws-sdk-go/pull/2375))
+ * Adds an Expirer interface that Providers can implement, and add a suitable implementation to Expiry class used by most Providers. Add a method on Credentials to get the expiration time of the underlying Provider, if Expirer is supported, without exposing Provider to callers.
+ * Fix [#1329](https://github.com/aws/aws-sdk-go/pull/1329)
### SDK Bugs
+* `aws/ec2metadata`: bounds check region identifier before split ([#2380](https://github.com/aws/aws-sdk-go/pull/2380))
+ * Adds empty response checking to ec2metadata's Region request to prevent a out of bounds panic if empty response received.
+* Fix SDK's generated API reference doc page's constants section links ([#2373](https://github.com/aws/aws-sdk-go/pull/2373))
+ * Fixes the SDK's generated API reference documentation page's constants section links to to be clickable.
