Added logging to signing validation functions

added logging to signing validation functions (#136)

* added logging to signing validation functions

Internal import updates #1

• Beginning (and possible ending) of updates to facilitate internal package import

Sigv4a implementation

• Sigv4a signing support

ECS Credentials Provider Fixes

• Fixes some bugs and leaks with the ECS credentials provider

Allow TLS Context to be passed into providers

Support BYO_CRYPTO by allowing tls_ctx to be passed into providers. (…

…#126)

Previously, providers that needed an `aws_tls_ctx` would create one automatically. Some providers allowed the user to pass one in as an option, some didn't even offer the option.

To support BYO_CRYPTO, every credentials provider that might need an `aws_tls_ctx` needs to let the user pass one in. Also, `aws_tls_ctx` is an expensive object, so automatic behind-the-scenes creation should be discouraged.

Backwards compatible changes:
- `aws_credentials_provider_chain_default_options`: added `tls_ctx`. created automatically if not provided
- `aws_credentials_provider_profile_options`: added `tls_ctx`. created automatically if not provided

Breaking changes (but there are no bindings so who cares):
- `aws_credentials_provider_ecs_options`: replaced ~~use_tls~~ with optional `tls_ctx`
- `aws_credentials_provider_sts_web_identity_options`: added `tls_ctx`. it is required
- `aws_credentials_provider_sts_options`: `tls_ctx` is now required (used to be optional)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

New managed thread API

Convert to new managed thread system for threads that cannot be reliably explicitly joined.

Delegate credentials provider

• New "delegate" credentials provider makes it easy to define a provider in a high-level language

Updates for new event-loop API, improvements to retries.

v0.4.8

delegate credential provider (#117)

Update to new host resolver creation interface

• updates tests to use the new default host resolver creation function

Auth will now always initialize CAL

v0.4.6

Initializing aws-c-cal (#113)